Magnetic fields & induction worksheet with answers

Free printable Magnetic fields & induction worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

A solenoid 30 cm long carries 5 A. How many turns N must it have for a flux density of 25.13 mT inside?

I = 5 AL = 30 cmB = 25.13 mTμ₀ = 4π × 10⁻⁷ T·m/A

N =

2.Easy

A rectangular loop of 20 cm by 15 cm lies in a uniform magnetic field of 0.2 T. The field lines make an angle of 45° with the plane of the loop. Find the magnetic flux Φ through the loop.

B = 0.2 TA = 20 cm × 15 cm45° to the plane

Φ = mWb

3.Medium

A proton moves up the page through a uniform magnetic field pointing into the page. Click the direction of the magnetic force on it.

v: up the pageB: into the page

1up the page
2to the right
3down the page
4to the left

4.Medium

A metal rod 40 cm long slides at 2.5 m/s along two rails in a uniform field of 0.4 T into the page. The rails are joined by a resistor of 2.5 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.4 TL = 40 cmv = 2.5 m/sR = 2.5 Ω

I = mA

5.Hard

A short coil of 200 turns is wound tightly round the middle of a long solenoid of 2000 turns, length 20 cm and diameter 4 cm. Find their mutual inductance M.

N₁ = 2000N₂ = 200l = 20 cm⌀ = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

M = mH

6.Hard

A long air-core solenoid has 200 turns, a length of 20 cm and a diameter of 4 cm. Find its self-inductance L.

N = 200l = 20 cm⌀ = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. N = 1200
2. Φ = 4.243 mWb
3. to the left
4. I = 160 mA
5. M = 3.158 mH
6. L = 315.8 µH

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