Electromagnetism Flashcards

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1
Q

What do the arrows do in a magnetic field?

A

Point away from north.
Do not cross.
Must have direction.
Continuous.
The closer the lines, the stronger the force.

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2
Q

What are examples of magnetic materials?

A

Iron,cobalt,steel,nickel.

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3
Q

Fletchings left hand rule

A

First finger- field
Thumb- thrust or force.
Second- direction of conventional current.

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4
Q

Which way does a magnetic field travel?

A

North to south

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5
Q

How could you change the direction of the force?

A

Change the direction of the magnetic field.
Change the direction of the current

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6
Q

How could you increase the size of the force?

A

Increase the size of the current.
Increase the strength of the magnetic field.
Increase the length of the wire in the field.

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7
Q

What could be done to make a motor turn faster?

A

Increase current.
Add more turns.
Increase the magnetic flux density.

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8
Q

How could you create a larger current?

A

Stronger magnetic field.
More turns on the coil.
Move the magnet or wire faster.

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9
Q

What is electromagnetic induction?

A

To induce a voltage and cause current to flow in a wire you need to have a changing magnetic field beside a wire

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10
Q

Coil 1 is switched on

A

The ammeter at coil 2 deflects momentarily then returns to zero

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11
Q

Coil 1 and 2 stationary

A

Nothing will happen.
No deflection in ammeter.

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12
Q

Coil 1 moved

A

Ammeter deflects and then returns to zero

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13
Q

Coil 2 moved

A

Same as coil 1 moved

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14
Q

Coil 1 switching off

A

Deflection in coil 2 (opposite direction to coil 1) then back to zero

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15
Q

What is direct current? D.C

A

Flows around the circuit in only one direction and it keeps the same steady value the whole time.

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16
Q

What is alternating current? A.C

A

Flows around a circuit in continually changing directions.

+- 325

50 cycles per second- 50hz

17
Q

How can the size of a current be increased?

A

Increase the magnets power-magnetic flux density
Increase the number of turns of wire in the field.
Increase the speed that it’s turning at-angular velocity
Increase the coil length

18
Q

What is a transformer?

A

Is a device that allows for the sizes of voltages to be changed.
It consists of two wire coils with a common soft iron core as shown below.

19
Q

What is the formula for transformers?

A

Np/Ns = Vp/Vs

20
Q

Where are transformers used?

A

Power station.
Transmission lines.
Before electricity enters our homes.