Magnetism and Electromagnetism

Question 0

What is a magnetically soft material?

Answer 0

Magnetic materials easily demagnetised, used for transformers etc

Question 1

How do you demagnetise a material?

Answer 1

• Put it in a reversed magnetic field
• Drop it
• Heat it to beyond its curie point (

Question 2

What is it called when electricity is generated?

Answer 2

Electromagnetic induction

Question 3

For a 100% efficient transformer, input power = _______ _________

Answer 3

Input power= Output power

Question 4

Give three advantages of using electromagnetics

Answer 4

• Can change the strength
• Can turn them on or off
• Don’t necessarily break if you drop them

Question 5

What are the four magnetic materials?

Answer 5

Iron, steel, cobalt and nickel

Question 6

What do these symbols stand for?

Vp = Np
- -
Vs Ns

Answer 6

Voltage primary = no. turns primary
—————— ——————–
Voltage secondary No. Turns sec

Question 7

The force acting on a current carrying conductor in a magnetic field increases with…

Answer 7

• The strength of field

- The size of current

Question 8

What do the abbreviations AC and DC mean?

Answer 8

Alternating and direct current

Question 9

Input power= Output power. What assumption am I making about the transformer for this equation to be true?

Answer 9

100% efficient or no energy lodt

Question 10

Give three disadvantages of using electromagnetics?

Answer 10

• Require electricity, so expensive
• Electricity pollutes the environment
• More complicated than fixed magmets

Question 11

How do you generate a current in a coil of wire?

Answer 11

Move the coil through a magnetic field

Question 12

What is the correct description of a transformer?

Answer 12

Two could around an iron core with Alternating Current

Question 13

A step up transformer has ten primary coils and fifteen secondary coils. The output voltage is 300V. What is the input voltage?

Answer 13

200V

Question 14

How do you induce magnetism in a material?3

Answer 14

Place it in a strong magnetic firld

Question 15

Flemming’s ________ hand rule

Answer 15

Left

Question 16

Which one of these changes will NOT increase the voltage produced by a generator?

a) increasing the speed of rotation
b) having fewer turns on the coil
c) using strong magnets

Answer 16

b) having fewer turns on the coil

Question 17

What is a ferrous metal?

Answer 17

A metal containing iron, therefore often magnetic

Question 18

There is a ______ on a charged particle when it moves in a magnetic field as long as the motion is not ______ to the field

Answer 18

Force

Parallel

Question 19

For the transformer to work, the current need to be:

Answer 19

AC

Question 20

How can the voltage and current generated by a coil having a magnet passed through it be increased?

Answer 20

More coils, stronger magnet or faster movement

Question 21

What is a magnetically hard material?

Answer 21

Magnetic materials highly resistant to being demagnetised, used for permanent magnets eg electric motors, hard drives

Question 22

An ___ ___ in a conductor produces a magnetic field around it

Answer 22

Electric current

Question 23

Vp x Ip = Vs x Is

What is this?

Answer 23

Power conserved between the input and output of a transformer