Question

A 100 millihenry coil carries a current of 1 A. Energy stored in its magnetic field is

• A. 0.5 J
• B. 1 A
• C. 0.05 J
• D. 0.1 J

Answer 1

The Correct Option is C

 To find the energy stored in the magnetic field of a coil, we can use the formula for energy stored in an inductor, which is given by:

\(E = \frac{1}{2} L I^2\)

where:

• \(E\) is the energy in joules (J).
• \(L\) is the inductance in henrys (H).
• \(I\) is the current in amperes (A).

Given:

• Inductance, \(L = 100 \, \text{millihenry} = 0.1 \, \text{H}\)
• Current, \(I = 1 \, \text{A}\)

Substitute these values into the formula:

\(E = \frac{1}{2} \times 0.1 \times (1)^2\)

\(E = \frac{1}{2} \times 0.1 \times 1\)

\(E = 0.05 \, \text{J}\)

Therefore, the energy stored in the magnetic field of the coil is \(0.05 \, \text{J}\).

This matches the correct answer choice:

0.05 J

. The other options can be eliminated as incorrect based on the correct calculation of energy using the formula above.

 

Concept Tip: Energy stored in an inductor depends on both the current flowing through it and its inductance. This formula is directly applicable for problems regarding energy in electromagnetic circuits.