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Magnetic fields and induction
5 NET Physics questions with answers and explanations.
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Two long parallel wires carry current in the same direction. The force between them is:
- 1 Attractive
- 2 Repulsive
- 3 Zero
- 4 Alternating
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Correct answer: Attractive
Parallel currents in the same direction attract each other. Opposite currents repel.
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What is the magnetic field 0.1 m from a long straight wire carrying 5 A? (mu0 = 4 pi x 10^-7 T m/A)
- 1 1 x 10^-5 T
- 2 1 x 10^-7 T
- 3 5 x 10^-5 T
- 4 2 x 10^-6 T
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Correct answer: 1 x 10^-5 T
B = mu0 I / (2 pi r) = 2 x 10^-7 x 5 / 0.1 = 1 x 10^-5 T.
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What is the magnetic field inside a long solenoid with 1000 turns per metre carrying 2 A? (mu0 = 4 pi x 10^-7 T m/A)
- 1 2.5 x 10^-3 T
- 2 2.5 x 10^-5 T
- 3 8 x 10^-4 T
- 4 0.25 T
Show answer
Correct answer: 2.5 x 10^-3 T
B = mu0 n I = 4 pi x 10^-7 x 1000 x 2, which is about 2.5 x 10^-3 T.
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A magnetic field of 0.2 T is perpendicular to a loop of area 0.5 m2. What is the magnetic flux through the loop?
- 1 0.1 Wb
- 2 0.4 Wb
- 3 0.7 Wb
- 4 2.5 Wb
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A 0.2 m rod moves at 10 m/s at right angles to a magnetic field of 0.5 T. What emf is induced across it?
- 1 0.1 V
- 2 1 V
- 3 10 V
- 4 0.5 V