Gaokao Physics: Electromagnetism Flashcards
7 cards from real GAOKAO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Gaokao Physics: Electromagnetism flashcards as text
Two long parallel wires carry equal currents in the same direction. The magnetic force between them is:
Answer: Attractive
Parallel currents in the same direction attract each other; this is the basis of the original SI definition of the ampere.
A capacitor with capacitance 20 μF is connected to a DC source of 50 V. What charge is stored?
Answer: 1×10⁻³ C
Q = CV = 20×10⁻⁶ × 50 = 1×10⁻³ C.
In a solenoid, doubling the number of turns per unit length (while keeping current constant) changes the magnetic field inside by a factor of:
Answer: 2
B = μ₀nI; doubling n doubles B.
The unit of magnetic flux is:
Answer: Weber (Wb)
Magnetic flux Φ = BA is measured in Webers (Wb); 1 Wb = 1 T·m².
A positive charge moves in the direction of an electric field. Its electric potential energy:
Answer: Decreases
A positive charge moving along the field direction loses potential energy (like a mass falling in gravity).
A current of 5 A flows through a 10 Ω resistor for 2 minutes. The heat generated is:
Answer: 30,000 J
Q = I²Rt = 25 × 10 × 120 = 30,000 J.
Maxwell's equations predict that changing electric fields create:
Answer: Magnetic fields
Maxwell's displacement current concept shows that a time-varying electric field generates a magnetic field, just as a physical current does.