Chapter 21 - Electromagnetism. Flashcards Preview

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Flashcards in Chapter 21 - Electromagnetism. Deck (19)
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1
Q

Describe Han Oersted’s experiment and the result of experiment and what does it prove?

A

A simple electric circuit is set up with current running from south to north. Two compasses are placed on top and under the wire respectively.

The needle of the compass on top will turn to the east while the needle of the compass under the wire will turn to the west.

A magnetic effect is produced whenever there is a current flow

2
Q

In Han Oersted’s experiment, a larger current will result in a _______ deflection of the needle of the compass

A

Larger

3
Q

How to determine the magnetic field pattern around a CURRENT carrying conductor? e.g wire with current flowing

A

Use the right hand grip rule, the thumb point that the direction of the current flow, the other four fingers will indicate pattern of the field

4
Q

A Dot ( . ) indicates that the current direction is ?

A

coming to ‘you’

5
Q

A ( + ) indicates that the current is coming ?

A

going away from ‘you’

6
Q

The closer the field line, the _______ the magnetic field

A

Stronger

7
Q

Magnetic field pattern diagram refer to notes

A

okay

8
Q

What are the two method to increase the strength of the magnetic field

A

Increase the current

Increase the number of the turn of the solenoid

9
Q

A force on a current carrying conductor in a magnetic field can be produced because?

A

There are two magnetic field and they interact with each other

10
Q

How to determine the direction of the force produced by the interaction between magnetic field and current

A

Use the Fleming’s left hand rule.
The thumb represent the motion/force
The second finger represent the field
The middle finger represent the current

11
Q

What happen when two parallel wires with current flowing in the SAME direction are placed next to each other? Why?

A

The two wires will be attracted to each other.
The magnetic field of the two wire cancel out each other in the middle part, while the outer parts of the wires still have magnetic field, thus, the magnetic field strength of the outsides, is stronger then the inside, thus producing a force to push the wires inwards

12
Q

What happen when two parallel wires with current flowing in the OPPOSITE direction are placed next to each other? Why?

A

The two wires will repel each other.
The magnetic field of the two wire enhance each other in the middle part, thus, the magnetic field strength of the inside, is stronger then the outside, thus producing a force to push the wires outwards

13
Q

In a simple motor, how to increase the turning effect of the coil, 2 ways

A

increase the current

use stronger magnet with strong magnetic field

14
Q

How does a motor work? (Diagram refer to notes)

A

When the current pass through the coil, the coil turn in clockwise direction (Fleming’s left hand rule). when the coil finally come to rest in a vertical position. The commutators lose contact with the brushes and make contact with other half. This changes the current direction which in turn changes the force acting on the coil, making the coil continue to move in a clockwise direction. As the current direction is reversed every half a turn, the coil will continue to turn in clockwise direction, achieving the motor effect.

15
Q

What is the purpose of the commutator in a motor?

A

It reversed the current direction every half a turn so that the coil continues to turn in one direction ONLY

16
Q

What is the purpose of the carbon brushes in a motor?

A

It is to provide the electrical contact with the commutators for the current to flow

17
Q

What are the two situation where the charge do not experience a force/

A

When the charge itself is not moving (no current)

When the charge is move along the magnetic field line (no field)

18
Q

What is the situation where the charge do experience a force?

A

when the charge move across the field line

19
Q

How to determine the direction of the force exert on a moving charged particle?

A

Use Fleming’s left hand rule