- Take a long wire and bend it to form a circle.
- Pass the wire through the cardboard such that half the wire is above it and the remaining part of the wire is below the cardboard.
- Join the free ends of the wire to a battery through a plug key.
- Insert the key and pass the current. Sprinkle iron filings on the cardboard and tap gently.
- Concentric circles are formed, which are centred at the point where the wire passes through the cardboard.
- The lines near the centre of the loop are almost straight. The magnetic field at the centre of the loop is perpendicular to the plane of the loop.
- The concentric circles become larger as we move away from the wire
The EJSMagnetic Field from Loops model computes the B-field created by an electric current through a straight wire, a closed loop, and a solenoid. The user can adjust the vertical position of the slice through the 3D field.
- Watch the simulation as the field changes from the field around a long straight current-carrying wire to the field near a coil. Explain what happens to the field. Inside a coil of many loops, why is the field fairly uniform near the center (think about vector addition and what vectors would be adding together near the center).
- There is an arrow on each end of the wire (red and blue). Which one shows the direction of the current in the wire? Explain.
- The red arrows indicate the resultant direction of the magnetic field due to the loop.
- The blue arrows indicate the resultant direction of the individual segments of wire.
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