3.13 Electromagnetism Flashcards

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1
Q

As a current flows through a wire, a magnetic field is created around the wire. What is the magnetic field made of?

A

Concentric circles perpendicular to the wire, with the wire in the gender

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2
Q

How would magnetic fields around a circular coil work?

A

The magnetic fields would stretch out and form ellipses as they interact with each other. Also, as the magnetic fields combine they form a single magnetic field which runs straight through the centre of the coil.

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3
Q

How can you increase the strength of the magnetic field that a current-carrying wire produces?

A

By wrapping the wire into a coil called a solenoid

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4
Q

Describe a solenoid

A
  • You can increase the strength of the magnetic field that a current-carrying wire produces by wrapping the wire into a coil called a solenoid.
  • The magnetic field strength increases because the fields around each turn of wire line up with each other.
  • The magnetic field inside a solenoid is strong and uniform (it has the same strength and direction at every point in that region).
  • Outside the coil, the magnetic field is just like the one round a bar magnet
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5
Q

How can the magnetic effect of a solenoid be increased? (4)

A

By:
- Increasing the current through the coil
- Increasing the number of turns but keeping the length the same
- Decreasing the cross-sectional area of the solenoid
- Adding a block of iron in the centre of the coil. This iron core becomes an induced magnet whenever current is flowing, so the magnetic effect of the solenoid is increased.

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6
Q

What is a current-carrying solenoid with an iron core called?

A

An electromagnet - a magnet with a magnetic field that can be turned on and off by turning the current on and off

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7
Q

When electromagnets were discovered in the 19th century, it led to the creation of lots of devices. What is one example of these?

A

Electromagnetic relays

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8
Q

What did the electromagnetic relay invention lead to?

A

Huge advances in communications as they allowed coded messages to be sent long distances as electrical signals before being translated back into words (telegraphs).

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9
Q

How do electromagnetic relays work? (2)

A
  • When the switch in circuit one is closed, it turns on the electromagnet, which attracts the iron contact on the rocker.
  • The rocker pivots and pushes together the contacts, completing circuit two and generating an electrical signal.
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