Gaokao Exam Gaokao Physics: Electromagnetism 3

Question 1

Coulomb's law states that the force between two point charges is proportional to:

Accepted Answer

The product of the charges divided by the square of the distance

Answer

Coulomb's law: F = kq₁q₂/r², force proportional to charge product and inversely proportional to distance squared.

Question 2

The magnetic force on a current-carrying conductor of length L carrying current I in a field B at angle θ is:

Accepted Answer

F = BIL sinθ

Answer

The Ampere force is F = BIL sinθ, maximum when current is perpendicular to the field.

Question 3

A 10 μF capacitor is charged to 100 V. The energy stored in the capacitor is:

Accepted Answer

0.05 J

Answer

U = ½CV² = ½ × 10×10⁻⁶ × 100² = 0.05 J.

Question 4

When the distance between two parallel plates of a capacitor (connected to a battery) is doubled, the capacitance:

Accepted Answer

Halves

Answer

C = ε₀A/d; doubling d halves C.

Question 5

In an AC circuit, the root-mean-square (rms) voltage across a 10 Ω resistor is 20 V. The average power dissipated is:

Accepted Answer

40 W

Answer

P = V_rms²/R = 400/10 = 40 W.

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