Question:
The magnetic field energy in an inductor changes from maximum value to minimum value in 5 ms, when connected to an a.c. source. The frequency of the source is
The magnetic field energy in an inductor changes from maximum value to minimum value in 5 ms, when connected to an a.c. source. The frequency of the source is
Updated On: Feb 6, 2025
- 50 Hz
- 20 Hz
- 200 Hz
- 500 Hz
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The Correct Option is A
Solution and Explanation
Magnetic field energy of a coil is given by $\frac{1}{2} LI^2$
In this case I changes from maximum to zero value in 5 ms $i.e.$ in T/4 ms
$\therefore$ T/4 = 5 ms or T = 5 $\times$ 4 = 20 ms = $20 \times 10^{-3}$ s
Then, frequency $\nu = \frac{1}{T} = \frac{1}{20 \times 10^{-3}}$ = 50 Hz
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Concepts Used:
Inductance
Inductance is a key parameter in electrical and electronic circuit designs. Like resistance and capacitance, it is a basic electrical measurement that affects all circuits to some degree.
Inductance is used in many areas of electrical and electronic systems and circuits. The electronic components can be in a variety of forms and may be called by a variety of names: coils, inductors, chokes, transformers, . . . Each of these may also have a variety of different variants: with and without cores and the core materials may be of different types.
There are two ways in which inductance is used:
- Self-inductance: Self-inductance is the property of a circuit, often a coil, whereby a change in current causes a change in voltage in that circuit due to the magnetic effect of caused by the current flow. It can be seen that self-inductance applies to a single circuit - in other words it is an inductance, typically within a single coil. This effect is used in single coils or chokes.
- Mutual-inductance: Mutual inductance is an inductive effect where a change in current in one circuit causes a change in voltage across a second circuit as a result of a magnetic field that links both circuits. This effect is used in transformers.