# Forces and Electromagnetism

HideShow resource information
• Created by: Eloise
• Created on: 23-04-16 12:48
What's the force that keeps something moving in a circle?
Centripetal force
1 of 17
What three factors require a large centripetal force to keep it moving?
Small radius, Large mass and Fast moving
2 of 17
What's the definition of a magnetic field?
It's a region where magnetic materials and current carrying wires experience a force acting on them
3 of 17
What is an electromagnet?
A magnet whose magnetic field can be turned on or off with an electric current
4 of 17
What's the magnetic field like inside a solenoid and outside it? How do you increase the strength of it?
inside: strong and uniform Outside: concentric circles To increase strength you add a magnetically soft iron core
5 of 17
What is Flemmings left hand rule and what is it used for?
Thumb: motion. Forefinger: Magnetic field. Second finger: Current. Used for the mt
6 of 17
What is the motor effect?
The force experienced by a current carrying wire in a magnetic field
7 of 17
2 factors that speed up electric motors
More current and Stronger magnetic field
8 of 17
How can you reverse the direction of the force?
Swapping the polarity of the DC supply or swapping the magnetic poles
9 of 17
What's a split ring commuter?
It swaps the contacts every half turn to keep the motor rotating in the same direction
10 of 17
What is electromagnetic induction?
The creation of potential difference across a conductor which is experiencing a change in magnetic field
11 of 17
Name 2 examples of electromagnetic induction
1) moving a magnet in a coil of wire 2)moving a wire cutting through a magnets magnetic field
12 of 17
How do generators work?
Turning a magnet end to end inside a coil, as you turn the magnet the coils magnetic field changes and every half turn the magnetic field reverses, produces AC current
13 of 17
Describe a step up transformer and a step down transformer
Stepup: increases the voltage, more turns on secondary coil. Stepdown: decreases the voltage, more turns on the primary coil
14 of 17
Explain how a transformer works
The primary coil produces a magnetic field which stays in the iron core and passes through the secondary coil. Ac in the primary coil means field in iron core is constantly changing. The change induces an alternating voltage across secondary coil.
15 of 17
Why won't a transformer work with DC?
There would still be a magnetic field in the iron core however it isn't constantly changing so no induction will occur
16 of 17
What is a switch mode transformer?
It operates at higher frequencies so can be made much lighter and smaller as well as being much more efficient as they use very little power
17 of 17

## Other cards in this set

### Card 2

#### Front

What three factors require a large centripetal force to keep it moving?

#### Back

Small radius, Large mass and Fast moving

### Card 3

#### Front

What's the definition of a magnetic field?

### Card 4

#### Front

What is an electromagnet?

### Card 5

#### Front

What's the magnetic field like inside a solenoid and outside it? How do you increase the strength of it?