Free Electromagnetism MCQs with Answers
1,176 Electromagnetism MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Magnetic flux density and magnetic flux describe the strength of a magnetic field and the field passing through a surface. A charged particle moving through a magnetic field experiences a force perpendicular to its velocity and may follow circular or helical motion, depending on the angle between velocity and field.
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Read the Electromagnetism notesFree MDCAT chapter notes with key terms1,176 questions · page 21 of 59
- A. 4.8 A
- B. 9.6 A
- C. 2.4 A
- D. 1.2 A
Explanation: Voltage ratio in a transformer is Vs/Vp = Ns /Np. Thus, Vs = (50/200) × 240 = 60 V. Current in the secondary I = V /R = 60/10 = 6 A.
Correct answer: 4.8 A- A. 2.84 × 10⁻⁵ m
- B. 4.92 × 10⁻⁵ m
- C. 5.68 × 10⁻⁵ m
- D. 8.52 × 10⁻⁵ m
Explanation: The radius of a helical path is r = mv/(qB), where v = v sinθ is the velocity component perpendicular to the magnetic field.
Correct answer: 4.92 × 10⁻⁵ m- A. 20 V
- B. 40 V
- C. 80 V
- D. 100 V
Explanation: Induced emf = ε = NΔΦ/Δt, where Φ = BA, A = 0.1 × 0.1 = 0.01 m², ΔB = 0.5 - (-0.5) = 1 T, N = 40, Δt = 0.02 s.
Correct answer: 40 V- A. 2 × 10⁻⁶ T (out of plane)
- B. 4 × 10⁻⁶ T (into plane)
- C. 5.55 × 10⁻⁶ T (out of plane)
- D. 8 × 10⁻⁶ T (into plane)
Explanation: Magnetic field due to a long wire is B = (μoI)/(2πr). Distance r = √(0.22 + 0.32) = 0.36 m.
Correct answer: 5.55 × 10⁻⁶ T (out of plane)- A. 0.4 V
- B. 0.8 V
- C. 1.6 V
- D. 3.2 V
Explanation: Motional emf = ε = BlvN, where l is the length of the conductor moving perpendicular to the magnetic field.
Correct answer: 1.6 V- A. 72 W
- B. 180 W
- C. 288 W
- D. 360 W
Explanation: Voltage ratio Vs/Vp= Ns/Np. Thus, Vs= (100 / 400) × 240 = 60 V. CurrentIs =Vs/R= 60 / 20= 3A.Power P =VsIs=60×3=180 W, but adjusting for…
Correct answer: 180 W- A. 0.0157 m
- B. 0.0314 m
- C. 0.0628 m
- D. 0.0888 m
Explanation: Pitch = vT, where v = v cosθ, T= 2πm/(qB). For θ = 45°, v = 10 m/s, cos 45° = 1/√2, q = 4 × 10⁻⁶ C, m = 2 × 10⁻⁴ kg, B = 0.5 T: T = 2π(2 ×…
Correct answer: 0.0628 m- A. 7.85 × 10⁻⁵ Wb
- B. 1.57 × 10⁻⁴ Wb
- C. 3.14 × 10⁻⁴ Wb
- D. 6.28 × 10⁻⁴ Wb
Explanation: B = μ₀nI = (4π × 10⁻⁷)(500/0.4)(5) ≈ 7.85 × 10⁻³ T. Flux Φ = BA = 7.85 × 10⁻³ × 0.01 = 1.57 × 10⁻⁴ Wb.
Correct answer: 1.57 × 10⁻⁴ Wb- A. 0.15 A
- B. 0.3 A
- C. 0.6 A
- D. 1.2 A
Explanation: Motional emf = ε = Blv = 0.3 × 0.5 × 4 = 0.6 V. Induced current I = ε/R = 0.6/2 = 0.3 A.
Correct answer: 0.3 A- A. 4.02 V
- B. 8.04 V
- C. 16.08 V
- D. 32.16 V
Explanation: Induced emf = ε = NΔΦ/Δt, where Φ = BA cosθ, A = π(0.2)² = 0.1256 m², Δcosθ = (cos 0° - cos 90° = 1), B = 0.8 T, Δt = 0.1 s, N = 1.
Correct answer: 8.04 V- A. 50 V
- B. 100 V
- C. 200 V
- D. 400 V
Explanation: For an ideal transformer, power in = power out: VpIp = VsIs. Given Vp = 200 V, Ip = 2 A, power = 200 × 2 = 400 W.
Correct answer: 100 V- A. 2.19 × 10⁻⁷ s
- B. 4.38 × 10⁻⁷ s
- C. 6.57 × 10⁻⁷ s
- D. 8.76 × 10⁻⁷ s
Explanation: Time period T = 2πm/(qB). Substituting m = 1.67 × 10-27 kg, q = 1.6 × 10-19 C, B = 0.3T.
Correct answer: 2.19 × 10⁻⁷ s- A. 30 V
- B. 60 V
- C. 90 V
- D. 120 V
Explanation: Induced emf = ε = NΔΦ/Δt, where Φ = BA, A = 0.05 m², ΔB = 0.6 - 0 = 0.6 T, N = 30, Δt = 0.03 s.
Correct answer: 60 V- A. 3.84 × 10⁻⁴ N/m
- B. 7.68 × 10⁻⁴ N/m
- C. 1.92 × 10⁻⁴ N/m
- D. 5.76 × 10⁻⁴ N/m
Explanation: Force per unit length F/L = (μ₀I₁I₂)/(2πd). Substituting μ₀ = 4π × 10⁻⁷, I₁ = 8 A, I₂ = 12 A, d = 0.05 m.
Correct answer: 3.84 × 10⁻⁴ N/m- A. 0.4 V
- B. 0.346 V
- C. 1.2 V
- D. 1.6 V
Explanation: ε = B lv sin(θ)ε = 0.2 T x 0.4 m x 5 m/s xsin(60°) sin(60°) = √3/2 ≈ 0.866ε = 0.2 x 0.4 x 5 x 0.866 = 0.346 VRounded to two significant…
Correct answer: 0.346 V- A. 1 A
- B. 2 A
- C. 3 A
- D. 4 A
Explanation: For an ideal transformer, VpIp = VsIs and Vs /Vp = Ns /Np. Thus, Vs = (100/500) × 200 = 40 V. Power P = VsIs = 40 × 5 = 200 W.
Correct answer: 1 A- A. 56.5 V
- B. 113 V
- C. 169.5 V
- D. 226 V
Explanation: Peak emf = NBAω, where N = 50, B = 0.3 T, A = π(0.1)² = 0.0314 m², ω = 2πf = 2π × (1800/60) = 60π rad/s.
Correct answer: 113 V- A. 0.02 m
- B. 0.04 m
- C. 0.08 m
- D. 0.12 m
Explanation: Radius r = mv /(qB), where v = v sinθ = 4 × 10³ × sin 30° = 2 × 10³ m/s. Substituting m = 4 × 10⁻⁶ kg, q = 2 × 10⁻⁸ C, B = 0.1 T.
Correct answer: 0.08 m- A. 0.019 H
- B. 0.038 H
- C. 0.057 H
- D. 0.076 H
Explanation: Self-inductance L = μ₀n²Aℓ, where n = N/ℓ = 1000/0.8 = 1250 turns/m, A = 0.02 m², ℓ = 0.8 m.
Correct answer: 0.038 H- A. 0.2 A
- B. 0.4 A
- C. 0.8 A
- D. 1.2 A
Explanation: Motional emf = ε = Blv, where B = 0.5 T, l = 0.2 m, v = 10 m/s. Thus, ε = 0.5 × 0.2 × 10 = 1 V.
Correct answer: 0.4 A