Physics P3 3.2 The motor effect.

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What happens to the force in the motor effect if the current or the strength of the magnetic field is increased?
The force is increased.
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What direction is the force in the motor effect?
The force is at right angles to both the direction of the magnetic field and to the wire.
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What happens to the force in the motor effect if the direction of either the current or the magnetic field is reversed?
The force is reversed.
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What happens in an electric motor?
It has a coil which turns when a current is passed through it.
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What happens when we place a wire carrying an electric current in a magnetic field and what is this called?
It may experience a force and this is called the motor effect.
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How does the position of the wire affect the force?
The force is a maximum if the wire is at an angle of 90 degrees to the magnetic field and zero if the wire is parallel to the magnetic field.
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What is Fleming's left-hand rule used to determine?
The direction of the force using the thumb and first two fingers of the left hand.
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How is Fleming's left-hand rule used to determine the direction of the force using the thumb and first two fingers of the left hand?
The thumb and fingers are all held at right angles to each other: first finger represents the magnetic field (pointing north to south), second finger represents the current (pointing positive to negative), thumb represents the direction of the force.
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How can the size of the force be increased?
By increasing the strength of the magnetic force and/or increasing the size of the current.
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How is the direction of the force on the wire reversed?
If either the direction of the current or the direction of the magnetic field is reversed.
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Why does a coil spin when a current passes through it in an electric motor?
Because a force acts on each side of the coil due to the motor effect and the force on one side of the coil is in the opposite direction to the force on the other side.
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What reverses the direction of the current around the coil every half-turn in an electric motor and how?
The split-ring commutator because the sides swap over each half-turn, the could is always pushed in the same direction.
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What happens to the direction of the force on a wire carrying a current if the direction of the current and the magnetic field are both reversed?
It stays the same.
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The ends of the coil in a motor are parallel to the magnetic field. What is the size of the force on them?
Zero.
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**LOOK UP DIAGRAM OF FLEMING'S LEF-HAND RULE AND PRACTICE USING THIS RULE**
**LOOK UP DIAGRAM OF AN ELECTRIC MOTOR**
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Other cards in this set

Card 2

Front

What direction is the force in the motor effect?

Back

The force is at right angles to both the direction of the magnetic field and to the wire.

Card 3

Front

What happens to the force in the motor effect if the direction of either the current or the magnetic field is reversed?

Back

Preview of the front of card 3

Card 4

Front

What happens in an electric motor?

Back

Preview of the front of card 4

Card 5

Front

What happens when we place a wire carrying an electric current in a magnetic field and what is this called?

Back

Preview of the front of card 5
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