Electromagnetism 3: Motors Varqid

Electromagnetism 3: Motors

By Akram Varqid

Revision

Current will produce magnetic field

Magnetic field depend on current whether in wire or solenoid (coil)

Magnetic field is stronger when current is stronger

Direction of magnetic field can be determined using right hand rule

Magnetic field will combine making it stronger / weaker

Force can be determined using left hand rule​

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Part 1: Single wire

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Multiple Choice

If current coming out of page, it can be drawn as

• A dot in a circle

• An x in a circle

Multiple Choice

If magnetic field coming out of page, it can be drawn as

• A dot in a circle

• An x in a circle

Multiple Choice

If current coming into page, it can be drawn as

• A dot in a circle

• An x in a circle

Multiple Choice

A wire coming out of page, and magnetic field from left to right. The force will be

• Upward

• Downward

• Left

• Right

Multiple Choice

A wire coming into page, and magnetic field from left to right. The force will be

• Upward

• Downward

• Left

• Right

Multiple Choice

A wire coming into page, and magnetic field from right to left. The force will be

• Upward

• Downward

• Left

• Right

Multiple Choice

A wire coming out of page, and magnetic field from right to left. The force will be

• Upward

• Downward

• Left

• Right

Part 2: Double wire

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Multiple Choice

Magnetic field from left to right

Left wire out of page

Right wire out of page

Where is the force for each wire?

• Away from each other

• Toward each other

• Both upward

• Both downward

Multiple Choice

Magnetic field from left to right

Left wire into page

Right wire into page

Where is the force for each wire?

• Away from each other

• Toward each other

• Both upward

• Both downward

Multiple Choice

Magnetic field from left to right

Left wire into page

Right wire out of page

Where is the force for each wire?

• Left up right down

• Left down right up

• Both upward

• Both downward

Multiple Choice

Magnetic field from left to right

Left wire out of page

Right wire out of page

Where is the force for each wire?

• Left up right down

• Left down right up

• Both upward

• Both downward

Multiple Choice

Magnetic field from left to right

Left wire out of page

Right wire into page

Where is the force for each wire?

• Left up right down

• Left down right up

• Both upward

• Both downward

Multiple Choice

Magnetic field from right to left

Left wire out of page

Right wire into page

Where is the force for each wire?

• Left up right down

• Left down right up

• Both upward

• Both downward

Part 3: Double wire fixed

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Two wire fixed means they cant leave each other

So if one goes up and one goes down, it rotate

Direction of rotation depend on which wire up or down

If both wire up or both wire down, no rotation. The force cancel each other​

Usually use one single wire as coil going into page at one side then coming out at another side​

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Multiple Choice

Magnetic field from left to right

Left wire out of page

Right wire into page

Where is the force for each wire?

• Clockwise

• Counter clockwise

Multiple Choice

Magnetic field from left to right

Left wire into page

Right wire out of page

Where is the force for each wire?

• Clockwise

• Counter clockwise

Multiple Choice

Magnetic field from right to left

Left wire into page

Right wire out of page

Where is the force for each wire?

• Clockwise

• Counter clockwise

Multiple Choice

Magnetic field from right to left

Left wire out of page

Right wire into page

Where is the force for each wire?

• Clockwise

• Counter clockwise

Motor

We can convert electrical energy to kinetic

You can make a fan, a tyre, a pump or anything else that rotate at a switch of a button

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1. Coil of wire with current flow

2. Magnetic field from permanent magnet

3. Commutator

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Component of motor

1. Current flow from one side (top side)

2. M field from N to S

3. Force on top is up and the other is down

4. Coil rotates

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How motor works

1. Current enter from left side of commutator

2. Coil rotate to another side

3. Although commutator switch side, current still enter from left side

4. Rotation direction maintain

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Commutator?

1. If there is no commutator, when it rotate to next side, current enter from the right

2. So rotation will reverse back

3. No complete rotation will happen

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Commutator?

1. This is called a DC motor, it used Direct Current (DC) and it needed Split Ring commutator

2. AC Motor requires Slip Ring commutator

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Commutator?

Increasing motor speed

Factor affecting rotation speed

Amount of current or resistance

Strength of magnetic field

​Amount of coil loop​

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