Gaokao Exam Gaokao Physics: Electromagnetism 4

Question 1

Three resistors of 6 Ω, 3 Ω, and 2 Ω are connected in parallel. What is the equivalent resistance?

Accepted Answer

1 Ω

Answer

1/R = 1/6 + 1/3 + 1/2 = 1/6 + 2/6 + 3/6 = 1; R = 1 Ω.

Question 2

A wire of resistance R is stretched to twice its original length. Its new resistance is:

Accepted Answer

4R

Answer

Stretching to twice the length doubles L and halves cross-sectional area A (volume conserved); R = ρL/A increases by factor 4.

Question 3

A uniform electric field E = 500 V/m exists between two parallel plates separated by d = 0.02 m. The potential difference between the plates is:

Accepted Answer

10 V

Answer

V = Ed = 500 × 0.02 = 10 V.

Question 4

According to the right-hand screw rule, the magnetic field lines around a straight current-carrying wire form:

Accepted Answer

Concentric circles in planes perpendicular to the wire

Answer

By Ampere's law, the magnetic field around a long straight wire forms closed circular loops centred on the wire.

Question 5

Electromagnetic induction was discovered experimentally by:

Accepted Answer

Michael Faraday

Answer

Faraday discovered electromagnetic induction in 1831 through experiments with changing magnetic flux.

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