Electromagnetism (chapter 20)

Increasing strength of a magnetic field in a solenoid

• increasing the current flowing through the solenoid

• Increasing the number of turns per unit length of the solenoid

• placing a soft iron core within the solenoid

Electromagnets

1. Under normal conditions, when the switch is turned on, current slows through the solenoid.

2. When the current is below the limit, the magnetic field of the solenoid is weak and does not attract the iron bolt.

3. The solenoid and iron bolt are not in contact. The current flows normally through the circuit,

4. A surge in current occurs when there is a fault.

5. If the surge in current exceeds the limit, the solenoid becomes an electromagnet that is strong enough to attract the iron bolts.

6. As a result, the plastic plunger is free to move upward as the spring around the plunger extends. This action opens up the circuit and cuts the flow of current to the home appliances as well as the solenoid.

Increasing Turning effect of electric motors

• increasing the number of turns in the coil

• increasing the current

• adding a soft iron cylinder.

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