Question

What happens to the current in a magnetic coil while accelerating it's magnetic field

• A. Zero
• B. Decreases
• C. Constant
• D. Increases

Answer 1

Answer: (D)

Increases

Answer 2

Faraday's Law states induced EMF is proportional to the rate of change of magnetic flux ($\mathcal{E} \propto \frac{d\Phi_B}{dt}$). Current $I = \mathcal{E}/R$. "Accelerating its magnetic field" implies the rate of change of magnetic field ($\frac{dB}{dt}$) is increasing. Since $\Phi_B \propto B$, this means $\frac{d\Phi_B}{dt}$ is increasing. Consequently, the induced EMF and thus the induced current will increase.