Unit 6 - Magnetism

Question 1

how does motor work ??
why a current or a charged particle experiences a force in a magnetic field ??

Answer 1

the magnetic field produced by the current interacts with the magnetic field of magnet so the wire experiences a force

Question 2

how does generator work ??

Answer 2

rotation of coil will cut magnet when the wire cuts through the magnetic field an emf is induced
Fleming Right Hand Rule

Question 3

how does transformer work ?

Answer 3

1. the alternating current in the primary coil produces an alternating magnetic field.
2. when the secondary coil cuts the magnetic fieldlines 3.an emf is produced

Question 4

a moving charged object can be considered as a current . true or false

Answer 4

true

Question 5

if the particle is positive -> current is in the same direction as movement

Answer 5

true

Question 6

if particle is negative -> current is in the ———- (same/opposite) direction as movement

Answer 6

opposite

Question 7

describe how a student can demonstrate that a rod is charged

Answer 7

• get it close to another charged rod
• he will see a force on the rod

Question 8

describe an experiment to show that different rods have different types of charge.

Answer 8

• hang on rod freely
• get other rods on by one close to a hanged rod
• some will get attraction and some will get repulsion

Question 9

how can a student improve precision of his voltage measurement

Answer 9

use a more sensitive voltmeter

Question 10

how do you know the stregth of a magnetic feild chanes

Answer 10

the field lines are closer showing field strongest at poles

Question 11

how can you use 2 permeant magnets to produce a uniform magnetic field

Answer 11

• get the magnets close together
• opposite poles should be facing each other

Question 12

how to make a coil spin in the opposite direction

Answer 12

do any ONE of these
- reverse the direction of the current
- reverse the polarity of the supply
- reverse the direction of the magnetic feild by swapping the magnets

Question 13

suggest how to make the coil spin more slowly (related to motor effect)

Answer 13

• reducing the current
• reducing the supply voltage
• increasing the resistance of the circuit - this will reduce the current
• placing the coil in a weaker magnetic field -by using weaker magnets
• having fewer turns on the coil

Question 14

name a metal from which a permanent magnet is made up of

Answer 14

steel

Question 15

name a metal from which a soft magnet is made up of

Answer 15

iron and nickel

Question 16

In a transformer why is a very high voltage used

Answer 16

(1) higher voltage by transformer lowers the current
(2) the lower power loss I²R so lowering the current will reduce the power lost in cables as heat
(3) So we do not need to use thicker cables which are more expensive and we can use thinner cables

Question 17

another name for temporary manget

Answer 17

induced magnet

Question 18

whats the main difference between a permanent magnet and a temporary(induced) magnet

Answer 18

Permanent magnets (e.g. bar magnets) produce their own magnetic feld all the time.
Induced magnets only produce a magnetic feld when they’re in another, external magnetic feld.

Question 19

The stronger the magnetic feld at any
point, the closer together the feld lines are. True or False

Answer 19

True

Question 20

The force between a permanent and an induced magnet is always ——————

Answer 20

attractive

Question 21

explain magnetic feild line

Answer 21

imaginary lines used to represent strength and direction of the feild

Question 22

name some magnetization methods

Answer 22

1. induction
2. electric dc RGR(right hand grip)
3. stroking

Question 23

magnetization by induction

Answer 23

keeping it in contact with another magnet
only magnetically hard keep their magnetism

Question 24

magnetization by stroking

Answer 24

move the magnet along the object with the same pole and direction several times

Question 25

magnetization by electric dc rgr

Answer 25

iron around cardboard in coil and pass dc current

Question 26

how to increase strength of magnet formed by electric dc rgr

Answer 26

a. use larger current
2. increase no of turnings on coil

Question 27

an electric current around a …………… (conductor/insulator) produces a field around it

Answer 27

conductor

Question 28

How to use plotting compass to investigate magnetic feild

Answer 28

• place compass around magnet and note its direction;
• place compass in new position and note its direction again;
• directions linked together to find a field line