3b.3 - Magnetic Fields and The Motor Effect Flashcards

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1
Q

Define magnetic field

A

A region where magnetic materials and wires carrying currents experience a force acting on them

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2
Q

How can magnetic fields be represented?

A

Field diagrams

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3
Q

What do the field diagrams look for for a magnet?

A

A semi circle from the north pole to the south pole with arrows

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4
Q

What do you need to remember when drawing field diagrams?

A

Arrows

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5
Q

What way do arrows go on a magnetic field diagram?

A

North to south pole

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6
Q

Describe the magnetic field around a coil of wire

A

Concentric circles with a wire in the centre

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7
Q

What is a solenoid?

A

A coil of wire

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8
Q

What is the magnetic field like inside a coil of wire?

A

Strong and uniform

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9
Q

What is an electromagnet?

A

A magnet whose magnetic field can be turned on and off with an electric current

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10
Q

What does putting a magnetically soft iron core through the middle of the wire do to it?

A

Increase the strength of the magnetic field

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11
Q

What is a magnetically soft material?

A

A material that magnetises and demagnetises very easily

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12
Q

Where are electromagnets useful?

A

In cranes

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13
Q

What is the motor effect?

A

The force experienced by a current-carrying wire in a magnetic field

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14
Q

What happens to the force if the current is made bigger?

A

It is made bigger

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15
Q

What happens to the force if the magnetic field if made is made bigger?

A

It is made bigger

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16
Q

How is your hand positioned in Fleming’s left hand rule? (4)

A
  • Thumb up
  • First finger forward
  • Second finger right
  • Each at 90 degrees to each other
17
Q

What does the thumb stand for in Fleming’s left hand rule?

A

Motion

18
Q

What does the first finger stand for in Fleming’s left hand rule?

A

Field

19
Q

What does the second finger stand for in Fleming’s left hand rule?

A

Current

20
Q

How do simple electric motors work? (3)

A
  • Forces act in opposite directions on the two side arms in the coil of wire
  • The coil is on a spindle and the opposite directions make it rotate
  • The split ring commutator swaps the contacts every half turn to keep the motor turning in the same direction
21
Q

How can the direction of the motor change? (2)

A
  • Swapping the polarity of the direct current supply

- Swapping the magnetic poles

22
Q

Which two factors speed up a motor? (2)

A
  • More current

- Stronger magnetic field

23
Q

Where are motors used?

A

Fans, CD players etc.