Gaokao Exam Gaokao Physics: Electromagnetism 1

Question 1

Two point charges of +2 μC and +8 μC are separated by a distance of 0.30 m in vacuum. At what point along the line joining them is the electric field zero?

Accepted Answer

0.10 m from the +2 μC charge

Answer

0.10 m from the +8 μC charge

Answer

0.15 m from each charge

Answer

0.20 m from the +8 μC charge

Question 2

A proton moves with velocity 3×10⁶ m/s perpendicular to a uniform magnetic field of 0.20 T. What is the radius of the circular orbit? (mp = 1.67×10⁻²⁷ kg, e = 1.6×10⁻¹⁹ C)

Accepted Answer

0.157 m

Answer

0.314 m

Answer

0.628 m

Answer

0.078 m

Question 3

A rectangular coil of 100 turns with area 0.04 m² rotates at 50 rev/s in a uniform magnetic field of 0.5 T. What is the maximum EMF induced?

Accepted Answer

628 V

Answer

314 V

Answer

200 V

Answer

1256 V

Question 4

According to Lenz's law, when a bar magnet's north pole approaches a horizontal conducting loop from above, the induced current in the loop, viewed from above, flows:

Accepted Answer

Counterclockwise to oppose the increasing flux

Answer

Clockwise to oppose the increasing flux

Answer

In no specific direction

Answer

Alternating rapidly

Question 5

In a series RLC circuit, R = 40 Ω, X_L = 70 Ω, X_C = 40 Ω. What is the impedance of the circuit?

Accepted Answer

50 Ω

Answer

70 Ω

Answer

110 Ω

Answer

30 Ω

Question 6

Two parallel plate capacitors, each with capacitance C, are connected in series to a battery of EMF ε. The energy stored in the combination is:

Accepted Answer

Cε²/4

Answer

Cε²/2

Answer

Cε²

Answer

2Cε²

Question 7

A conducting rod of length 0.5 m moves at 4 m/s perpendicular to a uniform magnetic field of 0.8 T. The induced EMF is:

Accepted Answer

1.6 V

Answer

0.8 V

Answer

3.2 V

Answer

0.4 V