1.Easy
A rectangular loop of 8 cm by 30 cm lies in a uniform magnetic field of 0.3 T. The field makes an angle of 0° with the normal of the loop. Find the magnetic flux Φ through the loop.
B = 0.3 TA = 8 cm × 30 cm0° to the normal
Φ = mWb
Magnetic fields & induction worksheet with answers
2.Easy
A flat circular coil of 5 turns and radius 15 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.
N = 5I = 1.5 AR = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
A coil of 100 turns has an area of 20 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.3 T, which is perpendicular to its plane, in 500 ms. Find the average induced emf ε.
N = 100A = 20 cm²B = 0.3 TΔt = 500 ms
ε = mV
4.Medium
A coil of 25 turns has an area of 25 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.4 T, which is perpendicular to its plane, in 50 ms. Find the average induced emf ε.
N = 25A = 25 cm²B = 0.4 TΔt = 50 ms
ε = V
5.Hard
A deuteron starts from rest, is accelerated through a potential difference of 10000 V and then enters a uniform magnetic field of 0.25 T at right angles. Find the radius r of its path in the field.
m = 3.344 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 10000 VB = 0.25 T
r = cm
6.Hard
The current in a 10 mH inductor changes steadily from 0.5 A to 2 A in 1 ms. Find the magnitude of the self-induced emf ε.
L = 10 mH0.5 A → 2 AΔt = 1 ms
ε = V
Answer key
- 1. Φ = 7.2 mWb
- 2. B = 31.42 µT
- 3. ε = 240 mV
- 4. ε = 1 V
- 5. r = 8.173 cm
- 6. ε = 15 V
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