NUMS — Medical & Dental Entry Test

NUMS Physics — Electricity and Magnetism (Set 1)

Take the NUMS Physics — Electricity and Magnetism (Set 1): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer review. Covers…

What this test covers

30 NUMS Physics

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. Two point charges repel each other with a force F. If the distance between them is halved, what will the force become?
- A. 2F
- B. F/2
- C. 4F ✓
- D. F/4
Answer: C. 4F
Explanation: Coulomb's law F ∝ 1/r²; halving r multiplies the force by 2² = 4.
Q2. What is the electric field strength 0.3 m from a point charge of +2 μC in air? (k = 9 × 10⁹ N m² C⁻²)
- A. 6 × 10⁴ N C⁻¹
- B. 2 × 10⁵ N C⁻¹ ✓
- C. 2 × 10⁴ N C⁻¹
- D. 6 × 10⁵ N C⁻¹
Answer: B. 2 × 10⁵ N C⁻¹
Explanation: E = kq/r² = 9 × 10⁹ × 2 × 10⁻⁶/0.09 = 2 × 10⁵ N C⁻¹.
Q3. For an isolated +2 μC point charge, find the potential (work done per unit positive charge brought from infinity) at a point 30 cm away. (k = 9 × 10⁹ N m² C⁻²)
- A. 6 × 10⁴ V ✓
- B. 2 × 10⁵ V
- C. 1.8 × 10⁴ V
- D. 6 × 10³ V
Answer: A. 6 × 10⁴ V
Explanation: V = kq/r = 9 × 10⁹ × 2 × 10⁻⁶/0.3 = 6 × 10⁴ V.
Q4. How much work is needed to move a charge of 5 μC between two points on the same equipotential surface?
- A. Zero ✓
- B. Equal to the charge times the field strength
- C. Depends on the path taken
- D. 5 μJ
Answer: A. Zero
Explanation: W = qΔV and ΔV = 0 between points on an equipotential surface, so no work is done.
Q5. A slab of dielectric with relative permittivity 5 completely fills the gap of an air-filled parallel-plate capacitor. What happens to its capacitance?
- A. It becomes 5 times larger ✓
- B. It stays the same
- C. It becomes 25 times larger
- D. It becomes 5 times smaller
Answer: A. It becomes 5 times larger
Explanation: C = εᵣε₀A/d, so C increases by the factor εᵣ = 5.

The other 25 questions

Take the timed test (free, no sign-up) to see your score and the answer and explanation for every question.

Q6. A defibrillator's 100 μF capacitor is charged to 2000 V. How much energy is stored for the shock?
- A. 100 J
- B. 200 J
- C. 0.2 J
- D. 400 J
Q7. Two 4 μF capacitors are connected in series. What is the equivalent capacitance?
- A. 16 μF
- B. 2 μF
- C. 4 μF
- D. 8 μF
Q8. In a cathode-ray tube, electrons leaving the hot filament are pulled across a 100 V gap between cathode and anode. What kinetic energy, in joules, does each electron acquire? (e = 1.6 × 10⁻¹⁹ C)
- A. 1.6 × 10⁻²¹ J
- B. 1.6 × 10⁻¹⁹ J
- C. 1.6 × 10⁻¹⁷ J
- D. 100 J
Q9. A current of 2 A flows through a heating coil for 5 s. How many electrons pass any cross-section of the coil? (e = 1.6 × 10⁻¹⁹ C)
- A. 6.25 × 10¹⁸
- B. 6.25 × 10¹⁹
- C. 3.2 × 10¹⁸
- D. 1.6 × 10¹⁹
Q10. A wire is stretched so that its length doubles and its cross-sectional area halves. What happens to its resistance?
- A. It doubles
- B. It halves
- C. It stays the same
- D. It becomes four times
Q11. Resistors of 6 Ω and 3 Ω are connected in parallel. What is their combined resistance?
- A. 0.5 Ω
- B. 4.5 Ω
- C. 2 Ω
- D. 9 Ω
Q12. A sterilising heater is rated 1100 W, 220 V. What is the resistance of its element when operating normally?
- A. 0.2 Ω
- B. 242 Ω
- C. 5 Ω
- D. 44 Ω
Q13. A portable suction pump of resistance 5 Ω runs from a 12 V battery whose internal resistance is 1 Ω. What voltage is actually available across the pump's terminals?
- A. 2 V
- B. 11 V
- C. 10 V
- D. 12 V
Q14. Kirchhoff's first (junction) rule — the sum of currents into a junction equals the sum out of it — is a consequence of the conservation of:
- A. Momentum
- B. Energy
- C. Mass
- D. Charge
Q15. A Wheatstone bridge with resistors P, Q, R and S is balanced, so the galvanometer shows no current. Which relation holds?
- A. P/R = S/Q
- B. P × Q = R × S
- C. P + Q = R + S
- D. P/Q = R/S
Q16. As the temperature rises, how does the resistance change for a copper wire and for a pure silicon thermistor?
- A. Copper's increases; silicon's decreases
- B. Both increase
- C. Both decrease
- D. Copper's decreases; silicon's increases
Q17. A proton moves through a uniform magnetic field. In which situation does it experience no magnetic force?
- A. When it moves at 45° to the field
- B. When its speed is doubled
- C. When it moves perpendicular to the field
- D. When it moves parallel to the field lines
Q18. A charged particle moves in a circle perpendicular to a uniform magnetic field. If its speed is doubled, the radius of its path will:
- A. Become four times
- B. Double
- C. Stay the same
- D. Halve
Q19. A 0.1 m length of wire carrying 2 A lies perpendicular to a uniform magnetic field of 0.5 T. What force acts on it?
- A. 0.1 N
- B. 1.0 N
- C. 0.25 N
- D. 10 N
Q20. An MRI scanner uses a long solenoid. For a solenoid with 1000 turns per metre carrying 2 A, what is the magnetic field inside? (μ₀ = 4π × 10⁻⁷ T m A⁻¹)
- A. 2.5 × 10⁻⁶ T
- B. 8.0 × 10⁻³ T
- C. 1.3 × 10⁻³ T
- D. 2.5 × 10⁻³ T
Q21. How is a moving-coil galvanometer converted into an ammeter?
- A. By connecting a low resistance (shunt) in parallel with it
- B. By connecting a high resistance in parallel with it
- C. By connecting a high resistance in series with it
- D. By connecting a low resistance in series with it
Q22. The magnetic flux through a 100-turn coil changes by 0.02 Wb in 0.1 s. What emf is induced in the coil?
- A. 20 V
- B. 200 V
- C. 0.2 V
- D. 2 V
Q23. Lenz's law states that an induced current opposes the change producing it. This law is a direct consequence of the conservation of:
- A. Charge
- B. Magnetic flux
- C. Energy
- D. Momentum
Q24. A transformer in a hospital device steps 220 V mains down to 11 V. If the primary coil has 2000 turns, how many turns does the secondary have?
- A. 10
- B. 200
- C. 40000
- D. 100
Q25. An alternating voltage has a peak value of 311 V. What is its rms value?
- A. 440 V
- B. 220 V
- C. 156 V
- D. 311 V
Q26. As the frequency of an AC supply increases, how do the reactances of a pure inductor and a pure capacitor change?
- A. Both increase
- B. Inductive reactance increases; capacitive reactance decreases
- C. Inductive reactance decreases; capacitive reactance increases
- D. Both decrease
Q27. A changing current in one coil induces an emf in a nearby coil. What is this phenomenon called?
- A. Thermionic emission
- B. Electrostatic induction
- C. Mutual induction
- D. Self-induction
Q28. Why are the cores of transformers made of thin insulated laminations rather than solid iron?
- A. To increase the magnetic flux leakage
- B. To increase hysteresis loss
- C. To reduce energy loss due to eddy currents
- D. To reduce the weight of copper wire
Q29. A 10 kΩ resistor is connected in series with a 100 μF capacitor in an ECG filter circuit. What is the time constant of the circuit?
- A. 1000 s
- B. 10 s
- C. 1 s
- D. 0.1 s
Q30. The property ρ in R = ρL/A depends only on the material of a wire. In which SI unit is ρ measured?
- A. Ω m⁻¹
- B. S m⁻¹
- C. Ω m⁻²
- D. Ω m