Physics Practice Problems

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Written questions with full solutions that I’ve created for students in the past:

These multiple choice quizzes were drafted with AI assistance and then carefully revised by me. I hope they give you a fun challenge and a chance to see the concepts from new angles!

1. A double-slit experiment uses green light (λ = 530 nm) and produces bright fringes 5 mm apart on a screen 2 m away. The setup is then repeated with red light (λ = 650 nm). What happens to the fringe spacing?

A) Increases, because Δy ∝ λ
B) Decreases, because red light has lower energy
C) Stays the same (only slit separation matters)
D) Becomes irregular due to chromatic aberration

2. A soap bubble (n = 1.33) reflects white light. A region appears yellow (λ ≈ 580 nm) due to constructive interference. What is the minimum thickness of the bubble’s film at this point?

A) 109 nm
B) 218 nm
C) 580 nm
D) 1160 nm

3. A diffraction grating with 500 lines/mm is illuminated by a laser. The 2nd-order maximum appears at 30°. What is the wavelength of the laser?

A) 250 nm
B) 500 nm
C) 750 nm
D) 1000 nm

4. Unpolarized light passes through three polarizers: Vertical, At 45° to vertical, Horizontal. What fraction of the initial intensity emerges?

A) 0%
B) 6.25%
C) 25%
D) 12.5%

5. An X-ray beam (λ = 0.1 nm) strikes a crystal, producing a 1st-order diffraction maximum at 15°. What is the spacing between atomic planes?

A) 0.19 nm
B) 0.39 nm
C) 0.52 nm
D) 1.03 nm

6. A photon with 3.1 eV energy strikes a metal with a 2.3 eV work function. What is the maximum kinetic energy of the ejected electron?

A) 0.8 eV
B) 2.3 eV
C) 3.1 eV
D) 5.4 eV

7. A single slit (width = 0.1 mm) is illuminated with 600 nm light, producing a diffraction pattern. How does the central maximum width change if the slit width doubles?

A) Halves
B) Doubles
C) Stays the same
D) Becomes four times narrower

8. A scientist observes that blue stars emit more ultraviolet radiation than red stars. Why does this align with blackbody radiation theory?

A) Blue stars have higher surface temperatures (Wien’s law).
B) Blue stars are larger (Stefan-Boltzmann law).
C) Red stars absorb UV light.
D) UV light is polarized in blue stars.

1. A laser beam passes from air (n = 1.00) into a mystery transparent material at 30°. The refracted angle is 20°. What is the critical angle for total internal reflection at a material–air interface?

A) 38.7°
B) 43.2°
C) 53.1°
D) No critical angle exists (n_material ≤ n_air)

2. A perfectly cylindrical glass rod (n = 1.5) is submerged in oil (n = 1.4). Light enters the rod’s end at an angle such that rays strike the sidewall above the critical angle. What happens to the light?

A) It refracts out immediately (no TIR possible).
B) It undergoes total internal reflection and stays trapped.
C) It disperses into a rainbow (due to chromatic aberration).
D) It exits parallel to the rod’s surface (grazing emergence).

3. A thin converging lens (f = 10 cm) and a diverging lens (f = -15 cm) are placed 5 cm apart. An object is placed 20 cm from the converging lens. Where is the final image formed?

A) 6.7 cm right of the diverging lens
B) 10 cm left of the diverging lens
C) At infinity (parallel rays)
D) No image forms (virtual object)

4. A prism splits white light into colors, and a second identical prism (reverse orientation) is used to recombine them. In practice the final beam may not be perfectly white. Why?

A) Tiny misalignment/path differences leave residual angular dispersion, so recombination is imperfect.
B) The prisms absorb some wavelengths.
C) Total internal reflection prevents recombination.
D) The exit beam is polarized.

5. A spherical mirror produces a magnified virtual image. The object is moved closer to the mirror. What happens to the image?

A) It becomes real and inverted.
B) It remains virtual but shrinks.
C) It disappears (no image forms).
D) It becomes diminished and real.

6. A fiber optic cable (n = 1.6) is bent into a hairpin turn (180° curve). Why does light still propagate without escaping?

A) The cable’s cladding has a lower n, preserving TIR.
B) Light slows down in bends, avoiding refraction.
C) The bend radius exceeds the critical curvature.
D) Light is absorbed and re-emitted in the curve.

7. A human eye (modeled as a lens) focuses on a near object, then a far one. How does the focal length adjust?

A) The lens thickens for near objects (shorter f).
B) The lens flattens for near objects (longer f).
C) The retina moves forward.
D) The cornea changes refractive index.

8. A compound microscope uses two lenses: objective (f = 5 mm) and eyepiece (f = 20 mm). How does magnification change if the eyepiece is replaced with f = 10 mm?

A) It doubles (eyepiece f halved).
B) It halves (inverse relationship).
C) It stays the same (objective dominates).
D) It becomes inverted.

9. A parabolic mirror focuses starlight to a single point, unlike a spherical mirror. Why does a spherical mirror fail to do this?

A) Spherical aberration spreads the focus.
B) Chromatic aberration disperses light.
C) The focal length varies with angle.
D) Diffraction limits resolution.

10. A lens focuses red and blue light at different points. What aberration is this, and how is it fixed?

A) Chromatic aberration; use an achromatic doublet.
B) Spherical aberration; use a parabolic lens.
C) Coma; adjust aperture size.
D) Distortion; use aspherical elements.

1. A guitarist plucks a string, producing a fundamental frequency f. They then press the string at the midpoint, halving its vibrating length, and pluck with the same effort so the input energy is unchanged. What happens to the pitch and intensity?

A) Pitch doubles (octave higher), intensity quadruples.
B) Pitch doubles, intensity stays approximately the same.
C) Pitch quadruples, intensity halves.
D) Pitch stays the same, intensity doubles.

2. A bat emits a 50 kHz ultrasound pulse toward a moth flying away at 10 m/s. The speed of sound is 340 m/s. What frequency does the moth detect? (Doppler formula: f' = f(v ± v₀)/(v ∓ vₛ))

A) 48.6 kHz
B) 50 kHz (no relative motion).
C) 51.5 kHz (higher due to motion).
D) 52.9 kHz (double Doppler shift).

3. A sound engineer measures a concert’s volume at 100 dB (10⁻² W/m²). The city’s noise ordinance allows 85 dB. By what factor must the intensity be reduced to comply?

A) 1.5× (linear scaling)
B) 10× (one order of magnitude)
C) 32× (15 dB = 10 log₁₀(I₁/I₂))
D) 100× (two orders of magnitude)

4. A tuning fork vibrates at 440 Hz in air (v = 343 m/s) and underwater (v = 1500 m/s). How does the wavelength change underwater?

A) It shortens (higher speed = shorter λ).
B) It lengthens proportionally to the speed increase.
C) It stays the same (frequency dominates).
D) It becomes infinite (sound can’t travel in water).

5. An opera singer shatters a wine glass by singing a sustained note. What physical phenomenon is most critical for this to occur?

A) High sound intensity (loudness).
B) Resonance at the glass’s natural frequency.
C) Ultrasonic frequencies.
D) Doppler shifting.

6. A jet flies at Mach 2 (680 m/s) at 10,000 m altitude, where sound speed is 300 m/s. What describes the shock wave produced?

A) A single sonic boom when the jet passes.
B) A continuous cone-shaped wavefront at angle sin⁻¹(1/Mach).
C) No shock wave—supersonic flight is silent.
D) Spherical waves propagating isotropically.

7. A sound wave travels through steel (v = 5000 m/s), water (v = 1500 m/s), and air (v = 343 m/s) of the same temperature. Rank the attenuation (energy loss) from highest to lowest.

A) Air > Water > Steel
B) Steel > Water > Air (faster = more loss).
C) Water > Air > Steel (density dependence).
D) All equal (same frequency).

8. Two identical speakers emit 500 Hz tones in phase and are placed along a straight line. A listener stands at a point of constructive interference on this line and then walks straight toward one speaker. What minimum distance must they move to reach the nearest point of destructive interference?

A) 17 cm
B) 34 cm
C) 68 cm
D) 85 cm

1. A submarine rests on the ocean floor, perfectly neutrally buoyant. To ascend, it pumps seawater from its ballast tanks. Why does this work?

A) Reducing mass decreases density, making it less than seawater.
B) The pumped water creates an upward thrust (action-reaction).
C) The submarine’s volume increases, lowering its specific gravity.
D) Seawater pressure decreases as tanks empty.

2. A blood clot narrows a vessel, reducing its radius by 50% (Poiseuille’s law: Q ∝ r⁴). What pressure difference is needed to maintain the original flow rate?

A) Half the original pressure.
B) Twice the original pressure.
C) 8 times the original pressure.
D) 16 times the original pressure.

3. A hurricane-strength wind blows over a curved roof at 150 mph. Why might the roof tear off?

A) High viscosity air "sticks" to the roof.
B) Bernoulli’s principle lowers external pressure.
C) Turbulence creates chaotic pressure spikes.
D) The Venturi effect increases density inside.

4. A hydraulic lift has pistons of area 1 cm² (input) and 100 cm² (output). If you push the input with 10 N of force, what output force is generated?

A) 10 N (Pascal’s law violates energy conservation).
B) 100 N (force scales with area ratio).
C) 1000 N.
D) 10,000 N (pressure is force × area).

5. A glass capillary tube is placed in water (high surface tension) and mercury (low surface tension). What happens in each liquid?

A) Water rises, mercury falls.
B) Both rise due to adhesion.
C) Both fall due to gravity.
D) Mercury rises, water falls.

6. An airplane wing has a cambered top surface and a positive angle of attack. How does this shape create lift?

A) Slows airflow above, increasing pressure
B) Speeds airflow above, reducing pressure.
C) Increases viscosity, "dragging" the wing up.
D) Creates turbulence to stabilize flight.

7. A syringe with a straight needle of radius r and length L ejects water horizontally from a fixed height h above the floor. The plunger force (pressure drop across the needle) is held constant. The jet lands 10 cm from the syringe. If the needle radius is halved, how far does the water travel?

A) 5 cm
B) 10 cm
C) 40 cm
D) 2.5 cm

8. A river narrows from 10 m wide to 5 m wide, with depth constant. How does the water’s speed change?

A) Halves (continuity equation).
B) Doubles.
C) Stays the same (depth dominates).
D) Quadruples (Bernoulli effect).

9. A droplet of water (high surface tension) and alcohol (low surface tension) are placed on a wax surface. Which forms a taller bead?

A) Water, due to stronger cohesive forces.
B) Alcohol, because it wets the surface better.
C) Both form identical beads (same volume).
D) Alcohol, due to lower viscosity.

10. A Venturi meter measures fluid speed in a pipe by comparing wide/narrow section pressures. If the pressure difference Δ𝑃 doubles, how does the speed change?

A) ×√2.
B) ×2 (linear dependence).
C) ×4 (quadratic dependence).
D) Unchanged (Δ𝑃 affects viscosity).

1. A high-altitude balloonist accidentally inflates their balloon indoors (at 1 atm, 25°C) with helium to 5 L, then releases it outdoors where the pressure is 0.5 atm and temperature is –30°C. What happens to the volume of the balloon?

A) It shrinks to <5 L because colder temperatures dominate.
B) It expands to >5 L because pressure drop dominates.
C) It stays at 5 L because competing effects cancel out.
D) It bursts immediately due to extreme conditions.

2. A chef uses a pressure cooker. After it reaches steady boiling at 2 atm (absolute), how does the average kinetic energy of water molecules inside compare to water boiling in an open pot at 1 atm?

A) Higher, because the boiling temperature is higher at 2 atm.
B) The same, because temperature is constant.
C) Lower, because collisions are more frequent.
D) Unpredictable—it depends on the food being cooked.

3. Neon (Ne) and nitrogen (N₂) are at the same temperature. The Ne atoms have about 1.2x the rms speed of N₂ molecules. What explains this?

A) Ne is lighter (lower molar mass), so it moves faster.
B) N₂ forms diatomic bonds that slow it down.
C) The experiment violates the equipartition theorem.
D) Ne is monatomic, while N₂ has rotational inertia.

4. A student plots PV/RT vs. P for 1 mol of gas at 300 K and gets a curve that starts at 1.0 but slopes downward. What does this imply about the gas?

A) It behaves ideally at all pressures.
B) Intermolecular attractions dominate (negative deviation).
C) Molecular volume effects dominate (positive deviation).
D) The gas is pure helium.

5. A deep-sea diver’s tank contains a mix of O₂ and He at high pressure. After a dive, the tank is left in the sun, heating the gas. Which component’s partial pressure increases the most?

A) O₂, because it’s heavier.
B) He, because it’s lighter and faster.
C) Both increase proportionally (Dalton’s law).
D) Neither—the total pressure stays constant.

6. A bike tire is inflated to 5 atm at 20°C. During a race, friction heats the tire to 50°C, and a tiny leak reduces the pressure to 4.5 atm. Approximately what fraction of gas molecules leaked out?

A) 10%
B) 18%
C) 25%
D) 50%

7. A scientist compares the van der Waals constants a (attraction) and b (volume) for CO₂ and He. Which gas has larger a and b values, and why?

A) CO₂—stronger London forces and larger molecular size.
B) He—smaller size allows tighter packing.
C) Both have identical a and b because they’re noble gases.
D) a is larger for He, but b is larger for CO₂.

8. A gas cylinder contains N₂ at high pressure. When the valve is opened, the gas escapes into a vacuum through a tiny hole (effusion). How would the rate of effusion change if the gas were replaced with CO₂ at the same pressure and temperature?

A) It would increase, because CO₂ is heavier and "pushes" harder.
B) It would decrease, because CO₂ molecules move slower on average.
C) It would stay the same, because pressure and temperature are identical.
D) It would fluctuate randomly due to collisions.

9. A meteorologist studies air rising in a thunderstorm. As the air parcel ascends rapidly, it expands without heat exchange (adiabatic process). What happens to the temperature of the air parcel?

A) It increases, because expansion does work on the surroundings.
B) It decreases, because the air does work to expand.
C) It stays constant, because no heat is exchanged.
D) It depends on humidity—this only applies to dry air.

10. A student measures the compressibility factor (Z = PV/nRT) of methane at high pressure and finds Z > 1. What does this imply about methane’s behavior under these conditions?

A) Attractive forces dominate, pulling molecules closer.
B) Repulsive forces dominate due to finite molecular volume.
C) Methane behaves ideally (Z ≈ 1) at all pressures.
D) The measurement is faulty—Z cannot exceed 1.

1. A proton moves at constant velocity v perpendicular to a uniform magnetic field B. What is the path of the proton?

A) Straight line (no deflection)
B) Parabolic trajectory
C) Circular motion in the plane perpendicular to B
D) Helical path along the field direction

2. A current-carrying wire is placed between the poles of a horseshoe magnet, experiencing a downward force. What will happen if the current direction is reversed?

A) The force becomes upward.
B) The force direction remains the same.
C) The force becomes zero.
D) The wire rotates 90°.

3. A loop of wire rotates at constant angular velocity in a uniform magnetic field (axis of rotation ⊥ B). When is the induced emf in the loop maximum?

A) When the loop’s plane is parallel to B
B) When the loop’s plane is perpendicular to B
C) When the loop is at 45° to B
D) The emf is constant over time

4. A charged particle enters a region with crossed E (electric) and B (magnetic) fields and moves straight without deflection. What must be true about the particle’s velocity?

A) v = E/B, and v ⊥ to both E and B
B) v = B/E, parallel to E
C) v = 0
D) v must be randomly oriented

5. A bar magnet is dropped vertically through a horizontal copper ring (closed, conducting). Neglect air resistance. How does the magnet's acceleration compare to g while it is passing through the ring?

A) Greater than g
B) Equal to g
C) Less than g
D) Depends only on the magnet's mass

6. Two parallel wires carry currents in the same direction. What is the force between them?

A) Attractive
B) Repulsive
C) Zero
D) Rotational

7. A solenoid with a steady current produces a uniform B field inside. An iron core is inserted. What happens to the magnetic field strength inside?

A) Increases, due to ferromagnetic alignment
B) Decreases, because iron shields the field
C) Remains unchanged
D) Oscillates rapidly

1. A physics student rubs a balloon against their hair, causing the balloon to stick to a neutral wall. They notice that after a few minutes, the balloon slowly falls off. Which of the following best explains why the balloon eventually detaches?

A) The wall becomes positively charged, repelling the balloon. B) The excess electrons on the balloon gradually leak into the air or wall. C) The balloon loses its charge due to gravitational force. D) The induced polarization in the wall weakens over time.

2. Two identical metal spheres on insulating stands are touched together. Sphere A has a charge of +3Q, and Sphere B is neutral. They are then separated. What is the final charge on each sphere?

A) +1.5Q on both spheres B) +3Q on Sphere A, 0 on Sphere B C) +3Q on Sphere A, –3Q on Sphere B D) +6Q on Sphere A, –3Q on Sphere B

3. A hollow, uncharged conducting sphere surrounds a point charge +Q at its center. What is the electric field inside the conductor (between the inner and outer surfaces)?

A) Zero B) Equal to the field due to +Q alone C) Radially outward and increasing with distance D) Radially inward due to induced charges

4. A Van de Graaff generator is used to charge a metal sphere to +50,000 V. A student touches the sphere while standing on an insulating stool. Why does their hair stand on end?

A) Their body becomes negatively charged, repelling electrons in the hair. B) Each hair strand acquires like charges, causing mutual repulsion. C) The electric field ionizes the air, creating a plasma. D) Frictional forces between hair strands generate static electricity.

5. A parallel-plate capacitor is connected to a battery and fully charged. The plates are then slowly pulled farther apart while the battery remains connected. What happens to the energy stored in the capacitor?

A) Decreases, because U=½CV² and C decreases while V stays fixed. B) Increases, because separating the plates requires external work C) Remains constant, because the battery maintains the voltage. D) Depends on the dielectric material.

6. Lightning strikes a tree, but a nearby bird on a power line is unharmed. Why is the bird safe?

A) The power line acts as a Faraday cage, shielding the bird. B) The bird’s small size minimizes charge accumulation. C) No potential difference exists along the bird’s body. D) Air resistance prevents current flow through the bird.

7. A proton and an electron are released midway between two oppositely charged plates. Which particle reaches a plate first?

A) The proton, because it has more mass. B) The electron, because it has less mass. C) Both reach at the same time, since |q| is equal. D) Neither – they oscillate between the plates.

8. A dipole is placed in a uniform electric field and aligned at 45° to the field lines. What happens when released?

A) It rotates to align with the field. B) It accelerates linearly along the field. C) It oscillates indefinitely at 45°. D) It remains stationary due to torque cancellation.

9. A charged oil droplet in a Millikan apparatus is suspended motionless when the electric field is E. If the field is doubled, what happens?

A) The droplet accelerates upward at g. B) The droplet accelerates downward at g. C) It remains stationary because the charge adjusts. D) It oscillates due to inertia.

10. A student argues: "If Coulomb’s law had a 1/r³ dependence instead of 1/r², Gauss’s law would still hold." Is this claim valid?

A) Yes, because Gauss’s law is independent of the r-dependence. B) No, because flux would depend on distance from the source. C) Only if the charge distribution is spherical. D) Only in a vacuum.

1. A book rests on a table inside an elevator. The elevator begins accelerating upward. How does the normal force (N) from the table on the book compare to the book’s weight (mg) during this acceleration?

A) N = mg B) N < mg C) N > mg D) N = 0

2. A car turns left at constant speed on a banked curve without slipping. Which force is primarily responsible for the centripetal force?

A) Gravity B) Friction C) The horizontal component of the normal force D) The vertical component of the normal force

3. Two astronauts (A and B) push off each other in zero gravity. Astronaut A has twice the mass of Astronaut B. How do their accelerations compare during the push?

A) A accelerates twice as much as B. B) B accelerates twice as much as A. C) Both accelerate equally. D) Neither accelerates (no gravity).

4. A block slides at constant velocity down a ramp inclined at angle θ. What is the coefficient of kinetic friction (μₖ) between the block and ramp?

A) μₖ = 0 B) μₖ = tan θ C) μₖ = sin θ D) μₖ = cos θ

5. A person stands on a scale in a stationary elevator. The scale reads 700 N. The elevator then accelerates downward at 2 m/s². What does the scale read during the acceleration? (g = 10 m/s²)

A) 560 N B) 700 N C) 840 N D) 0 N

6. A heavy crate is pushed at constant speed across a rough floor. Which statement is true about the forces acting on the crate?

A) The applied force is greater than the kinetic friction. B) The applied force equals the kinetic friction. C) The applied force is less than the kinetic friction. D) The normal force cancels the applied force.

7. A horse pulls a cart. The cart moves forward, but the horse’s hooves do not slip. Why does the cart accelerate forward?

A) The horse’s force on the cart is greater than the cart’s force on the horse. B) The ground exerts a forward static friction on the horse; the horse pulls the cart forward via the harness, so the system accelerates. C) The cart’s inertia is less than the horse’s. D) The horse and cart form an action-reaction pair with unequal accelerations.

8. A rocket accelerates upward in space (no gravity) by ejecting exhaust gas downward. How does the rocket’s acceleration change if the rate of gas ejection doubles (but exhaust speed remains the same)?

A) Acceleration doubles. B) Acceleration halves. C) Acceleration remains the same. D) Acceleration quadruples.

1. A rollercoaster car (mass m) starts at rest at height h on a frictionless track. Halfway down the first drop, its height is h/2 and speed is v. If the initial height were doubled to 2h, how would the speed at h (now halfway down) compare?

A) Same speed (v) B) √2 times faster (√2v) C) 2 times faster (2v) D) 4 times faster (4v)

2. A chef places a cold pan (20°C) on a stove. After 1 minute, the pan reaches 80°C. The stove’s burner transfers heat at a constant rate. Why does the temperature NOT rise linearly over time (e.g., to 160°C after 2 minutes)?

A) The pan’s thermal conductivity decreases as it heats up. B) Heat loss to the surroundings increases with temperature difference. C) The stove’s burner output drops after 1 minute. D) The pan’s specific heat capacity changes with temperature.

3. A bouncing ball loses 30% of its kinetic energy with each bounce. After 2 bounces, what fraction of its initial height will it reach?

A) 21% B) 40% C) 30% D) 49%

4. A cyclist pedals uphill at constant speed. The road is steep, and air resistance is negligible. How does the work done by gravity compare to the work done by the cyclist over the same distance?

A) Gravity does positive work; cyclist does no work. B) Gravity does negative work equal in magnitude to the cyclist’s positive work. C) Gravity does zero work; cyclist does all the work. D) Both do equal positive work.

5. An engine extracts 500 J from a hot reservoir and rejects 300 J to a cold reservoir per cycle. What is the maximum possible temperature (in Kelvin) of the cold reservoir if the hot reservoir is 400 K?

A) 150 K B) 200 K C) 240 K D) 300 K

6. A spring is compressed by a distance x and launches a block across a frictionless surface, giving it kinetic energy KE. The experiment is repeated, but this time the spring is compressed by 2x. How does the block’s new kinetic energy compare to the original KE?

A) The same (KE) B) 2 times greater (2KE) C) 4 times greater (4KE) D) 8 times greater (8KE)

7. A car climbs a steep hill at a constant speed. The engine’s power output is P. If the car’s speed doubles while climbing the same hill (still constant speed), how does the required power change? Assume air resistance is negligible.

A) Power remains P (no change). B) Power doubles (2P). C) Power quadruples (4P). D) Power increases by a factor of 8 (8P).

8. A pot of water is heated from 25°C to 100°C, then kept boiling for 5 minutes. Why does boiling require more energy than heating the water to 100°C?

A) Boiling increases the water’s specific heat capacity. B) Energy is used to break intermolecular bonds (phase change), not raise temperature. C) The stove’s efficiency drops at high temperatures. D) Steam carries away heat faster than liquid water.

9. A clay ball (mass m) strikes and sticks to a stationary block (mass 2m) on a frictionless surface. What fraction of the initial kinetic energy is lost as thermal energy/sound?

A) 1/3 B) 1/2 C) 2/3 D) 3/4

10. An ideal gas undergoes an isothermal expansion (constant temperature) in a cylinder, doing work W on the piston. Which statement is true about the gas’s internal energy (ΔU) and heat transfer (Q)?

A) ΔU > 0; Q = 0 B) ΔU = 0; Q = W C) ΔU < 0; Q = W D) ΔU = 0; Q = 0

1. You replace your phone’s 1 m USB-C charging cable (resistance = 0.20 Ω) with a 3 m cable made of the same copper but half the cross-sectional area. The wall adapter still supplies 5 V. Which statement best describes how the charging current will change?

A) It will stay the same because the adapter voltage is fixed. B) It will drop to about one-third because the cable is three times longer. C) It will drop to about one-sixth because resistance scales with length and inverse area. D) It will increase because the longer cable acts like a larger “antenna” for electrons.

2. A string of 40 “old-school” incandescent Christmas lights is wired in series across 120 V. One bulb burns out, opening its filament. Which statement best describes the effect on the remaining bulbs?

A) All bulbs go dark because the open filament breaks the only current path. B) All bulbs get brighter because the supply voltage redistributes. C) Brightness is unchanged; the circuit self-bypasses the faulty bulb. D) Half the bulbs go dark; the rest remain lit due to internal shunts.

3. A hospital defibrillator delivers a 200 J pulse through two adhesive pads. If the contact area of the pads is halved while the gel conductivity is unchanged, which circuit principle best explains the increased tissue damage?

A) Decreased capacitance between pads raises voltage. B) Current density rises because resistance is inversely proportional to area, increasing local power dissipation (I²R). C) The pulse duration lengthens, depositing more energy. D) Halving area creates an LC resonance that heats tissue.

4. A solar string has five identical PV panels in series feeding an inverter, and each panel includes a bypass diode. One panel becomes partially shaded so its current capability drops by ~60%. Which statement best describes the effect on total string power?

A) The shaded panel’s bypass diode conducts, so the string runs at nearly the unshaded current but with ~1/5 lower voltage; power drops by about 20%. B) String power falls ~60% because series current is limited by the weakest panel. C) Power is unchanged; the other panels force current through the shaded one. D) Voltage rises to compensate, so power stays constant.

5. You are troubleshooting a desktop PC that randomly reboots. You measure that the 12 V rail sags to 11 V only when a high-power graphics card is installed. Which interpretation is most consistent with basic circuit analysis?

A) The graphics card’s resistance is too high, starving itself of current. B) The power-supply’s internal resistance is significant; adding a heavy load causes a larger voltage drop across it. C) Kirchhoff’s Voltage Law is violated, indicating a faulty multimeter. D) The GPU induces back-EMF that subtracts from the 12 V line.

6. A 1,500 W space heater and a 1,500 W hair dryer are each rated for 120 V. The heater uses a thick nichrome coil; the dryer uses a long, thin coil. Which statement best explains why the hair dryer’s heating element glows red, while the space heater’s element barely glows?

A) The dryer’s thinner wire has higher resistance, so it operates at higher current. B) Both draw the same current; the dryer glows because its smaller surface area raises temperature for the same I²R power. C) The heater’s coil is made of a material with zero emissivity. D) The heater’s element is wired in parallel, reducing voltage across it.

7. A biomedical engineer models a patch of membrane as a 1 µF capacitor in parallel with a 100 MΩ resistor. The cell swells so that the membrane area doubles while thickness and material properties are unchanged. Which change to the equivalent circuit best captures this?

A) Capacitance doubles; resistance unchanged. B) Capacitance doubles; resistance halves C) Capacitance halves; resistance doubles D) Both capacitance and resistance are unchanged

8. Before handling sensitive microchips, technicians touch a grounded metal strip to discharge static. A student suggests using a large 10 MΩ resistor between the wrist strap and ground instead of a direct wire. Which statement best describes the main advantage of adding this resistor?

A) It prevents ground loops that could induce AC hum. B) It limits any accidental current through the body to a safe level while still allowing charge to bleed off. C) It speeds up discharge by creating a voltage divider. D) It filters high-frequency transients via inductive reactance.

Question 1: A car starts from rest and accelerates uniformly to 25 m/s in 10 seconds. It then travels at a constant speed of 25 m/s for 20 seconds before decelerating uniformly to rest in 5 seconds.

(a) What is the total distance traveled? (m)

(b) What is the overall average velocity for the entire trip? (m/s)

Question 2: A car travels a fixed distance where the first half of the distance is covered at 60 km/h and the second half at 80 km/h.

What is the car’s overall average velocity (in km/h) for the journey?

Question 3: Train A moves at a constant speed of 30 m/s and is 200 m ahead of Train B. At t=0, Train B (initially at rest) starts accelerating uniformly at 2 m/s^2 to catch up with Train A. How long (in seconds) will it take Train B to catch Train A?

Time to catch up (seconds):

Question 4: A boat has a speed of 12 km/h relative to the water. It aims to cross a river that is 500 m wide. The river current flows at 3 km/h, parallel to the banks.

(a) How long (in seconds) does it take the boat to cross if it points directly perpendicular to the banks?

(b) How far downstream (in meters) will the boat drift?

Question 5: A boat moves at 12 km/h relative to the water and wishes to cross a 600 m wide river. It points its bow at an angle upstream such that its resultant path is perpendicular to the banks. The river current is 4 km/h.

(a) At what angle (relative to the perpendicular) should the boat point upstream?

(b) How long (in seconds) will the crossing take?