"The superconducting magnet in a magnetic resonance imaging system consists of a solenoid with 5.6 H of inductance. The solenoid is energized by connecting it to a 1.2 V DC power supply. Starting from zero, how long does it take for the solenoid to reach its operating current of 100 A?"

7.8min

Explanation:

The potential difference across an inductor inductance L is

is change in curent in a time

so, time taken for the solenoid to reach it operating current is

Given that,

Inductance of solenoid is L = 5.6H

Voltage across solenoid is v(L) = 1.2L

Δi(L) = 100A

substitute the values in the formula

Time taken for the solenoid to reach it operating current is

= 466.6s

convert to minute

= 466.6 /60

= 7.77min

≅ 7.8min

whichever one it is, it's definitely not one that you included on the list you provided.

an electric circuit