Inductor Energy
Energy stored in an inductor magnetic field.
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Stored in the magnetic field
How it works
An inductor stores energy whenever current builds up in its magnetic field, and that stored energy depends on both the inductance and the square of the current. The 21/2 factor appears because the current does not jump to its final value instantly; more work is needed to increase the current as the magnetic field strengthens. Since the formula uses I b2, doubling the current makes the stored energy four times larger.
When to use it
Use this formula when you need to find how much energy is stored in a coil, solenoid, relay, transformer winding, or any circuit element with significant inductance. It is especially useful in transient analysis, power electronics, and electromagnetic energy calculations.
Worked example, step by step
Given: L = 0.80 H, I = 3.0 A Step 1: Write the formula: E = (1/2)LI^2 Step 2: Substitute the values: E = (1/2)(0.80)(3.0)^2 Step 3: Square the current: E = (1/2)(0.80)(9.0) Step 4: Multiply: E = 0.40 d7 9.0 = 3.6 J Final answer: The energy stored in the inductor is 3.6 joules.
Common mistakes to avoid
- Forgetting to square the current and using LI instead of LI^2
- Mixing up inductance units and using mH as if it were H
- Using the formula for the voltage across an inductor instead of the stored energy
Did You Know?
Sparks when you unplug an appliance come from an inductor's stored energy resisting the sudden cutoff.
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