Physics Electricity and Magnetism 4

Question 1

Which of Maxwell's equations states that magnetic monopoles do not exist?

Accepted Answer

∇·B = 0

Answer

Gauss's Law for magnetism, ∇·B = 0, implies there are no magnetic monopoles.

Question 2

A transformer has 200 primary turns and 50 secondary turns. If the primary voltage is 120 V, what is the secondary voltage?

Accepted Answer

30 V

Answer

V_s/V_p = N_s/N_p → V_s = 120 × (50/200) = 30 V.

Question 3

The Lorentz force law for a charge q moving with velocity v in fields E and B is:

Accepted Answer

F = q(E + v×B)

Answer

The full Lorentz force includes both electric and magnetic contributions: F = q(E + v×B).

Question 4

What is the direction of the induced current in a loop when the magnetic flux through it is decreasing?

Accepted Answer

In the direction that increases the flux (opposing the decrease)

Answer

By Lenz's Law, the induced current opposes the change in flux, so it flows to increase the decreasing flux.

Question 5

A charge of 3 μC is placed in an electric field of 2,000 N/C. What force does it experience?

Accepted Answer

Both A and B

Answer

F = qE = 3×10⁻⁶ × 2000 = 6×10⁻³ N = 0.006 N; A and B are the same value.

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