1.Easy
A rectangular loop of 12 cm by 25 cm lies in a uniform magnetic field of 0.25 T. The field makes an angle of 60° with the normal of the loop. Find the magnetic flux Φ through the loop.
B = 0.25 TA = 12 cm × 25 cm60° to the normal
Φ = mWb
Magnetic fields & induction worksheet with answers
2.Easy
A straight wire 100 cm long carries 6 A at an angle of 30° to a uniform magnetic field of 0.2 T. Find the magnitude of the force F on the wire.
B = 0.2 TI = 6 AL = 100 cmθ = 30°
F = N
3.Medium
An alpha particle moving at 2 × 10⁶ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 20.74 cm. Find the magnetic flux density B.
m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 2 × 10⁶ m/sr = 20.74 cm
B = T
4.Medium
Two long parallel wires 2 cm apart carry currents of 25 A and 5 A in opposite directions. Find the force per metre of length F/L between them.
I1 = 25 AI2 = 5 Ad = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
Two coils with self-inductances of 100 mH and 20 mH have a coupling coefficient of 0.3. The current in the first coil changes at 10 A/s. Find the emf ε induced in the second coil.
L1 = 100 mHL2 = 20 mHk = 0.3di/dt = 10 A/s
ε = V
6.Hard
A coil of 200 turns, 5 cm × 10 cm, rotates in a uniform field of 0.4 T about an axis perpendicular to the field. At what speed n (in revolutions per minute) must it turn to give an rms emf of 44.43 V?
N = 200A = 5 cm × 10 cmB = 0.4 TErms = 44.43 V
n = rpm
Answer key
- 1. Φ = 3.75 mWb
- 2. F = 0.6 N
- 3. B = 0.2 T
- 4. F/L = 1250 µN/m
- 5. ε = 0.1342 V
- 6. n = 1500 rpm
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