Magnetism And Electromagnetism

Question 1

Which direction do magnetic field lines point ?

Answer 1

From north to south

Question 2

What does the density of magnetic field lines show

Answer 2

The strength

Question 3

What is the right hand rule ?

Answer 3

• take your right hand
• point your thumb in the direction of the current
• curl your fingers around
• the magnetic field follows the direction of your fingers

Question 4

How can you effect the strength of the magnetic field around a current carrying wire ?

Answer 4

• increase the current

- wrap the wire into a coil

Question 5

Whats the motor effect ?

Answer 5

A charged particle moving through a magnetic field will experience a force , as long as its motion is not parallel to the field

Question 6

What is the left hand rule ?

Answer 6

• thumb =motion
• first finger =field direction
• second finger =current

Question 7

How can you increase the rate at which an electromagnetic motor turns ?

Answer 7

• increase number of loops
• increase strength of magnetic field
• increase current

Question 8

What is electromagnetic induction?

Answer 8

Movement of a wire through a magnetic field produces a current in that wire

Question 9

How can you increase the size of the induced voltage ?

Answer 9

• move the wire more quickly
• use a stronger magnet
• wrap the wire in a coil so more wire is moving through the magnet

Question 10

What is faradays law ld electromagnetic induction ?

Answer 10

The size of the induced voltage across the ends of a wire is directly proportional to the rate at which the magnet lines of flux are being cut

Question 11

Whats the frequency of the uk current ?

Answer 11

50hz

Question 12

Whats the relationship in transformers between voltage and number of turns of the coil

Answer 12

Input voltage. P coils
————– =———-
Output voltage. S coils

Question 13

What kind of current will transformers only work in ?

Answer 13

Ac

Question 14

What are the names and rules of the poles of a magnet ?

Answer 14

North pole points north geographically and the south pole points south geographically , opposites attract

Question 15

Whats the equation for efficiency ?

Answer 15

Efficiency= useful / total x 100

Question 16

How efficient are transformers

Answer 16

100%

Question 17

Whats the equation for power , current and voltage

Answer 17

P=i x v

Question 18

Whats the equation for efficiency ?

Answer 18

Efficiency= useful / total x 100

Question 19

How efficient are transformers

Answer 19

100%

Question 20

Whats the equation for power , current and voltage

Answer 20

P=i x v