Class 10 Physics simulations · Magnetic Effects of Electric Current

Magnetic field around a straight wire

A vertical wire passes through a card. Pass a current and see the circular field lines and the compass needles.

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What to notice

The field lines are concentric circles. Reversing the current reverses the compass needles; the field is weaker farther away.

Key relation

B = μ₀ I / (2π r) (right-hand thumb rule gives the direction)

Try this

Reverse the current. Then double the distance: by how much does B fall?

What you can change

• Current I (positive = upward): -10 to 10 A
• Distance of the compass r: 1 to 10 cm

More in Magnetic Effects of Electric Current

• Force on a current-carrying wire
• Magnetic field on the axis of a loop
• Bar magnet and compass
• Magnetic field inside a solenoid

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