Gaokao Exam Gaokao Physics: Electromagnetism 5

Question 1

Two long parallel wires carry equal currents in the same direction. The magnetic force between them is:

Accepted Answer

Attractive

Answer

Parallel currents in the same direction attract each other; this is the basis of the original SI definition of the ampere.

Question 2

A capacitor with capacitance 20 μF is connected to a DC source of 50 V. What charge is stored?

Accepted Answer

1×10⁻³ C

Answer

Q = CV = 20×10⁻⁶ × 50 = 1×10⁻³ C.

Question 3

In a solenoid, doubling the number of turns per unit length (while keeping current constant) changes the magnetic field inside by a factor of:

Accepted Answer

2

Answer

B = μ₀nI; doubling n doubles B.

Question 4

The unit of magnetic flux is:

Accepted Answer

Weber (Wb)

Answer

Magnetic flux Φ = BA is measured in Webers (Wb); 1 Wb = 1 T·m².

Question 5

A positive charge moves in the direction of an electric field. Its electric potential energy:

Accepted Answer

Decreases

Answer

A positive charge moving along the field direction loses potential energy (like a mass falling in gravity).

Gaokao Exam Practice Test