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Magnetic fields and induction
5 NET Physics questions with answers and explanations.
Printable worksheet with answer key
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Two long parallel wires carry current in the same direction. The force between them is:
- 1 Repulsive
- 2 Alternating
- 3 Attractive
- 4 Zero
Show answer
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? (μ₀ = 4 pi x 10⁻⁷ T m/A)
- 1 2 x 10⁻⁶ T
- 2 5 x 10⁻⁵ T
- 3 1 x 10⁻⁵ T
- 4 1 x 10⁻⁷ T
Show answer
Correct answer: 1 x 10⁻⁵ T
B = μ₀ 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? (μ₀ = 4 pi x 10⁻⁷ T m/A)
- 1 2.5 x 10⁻³ T
- 2 0.25 T
- 3 2.5 x 10⁻⁵ T
- 4 8 x 10⁻⁴ T
Show answer
Correct answer: 2.5 x 10⁻³ T
B = μ₀ 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 2.5 Wb
- 3 0.7 Wb
- 4 0.4 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 1 V
- 2 10 V
- 3 0.5 V
- 4 0.1 V