Physics Triple 2 Flashcards
What is a transformer?
An electrical device used to change alternating voltage
What is a electromagnet?
A magnet whose field can be turned of and on with an electric current
What is electromagnetic induction?
The process of inducing a potential difference in a wire by moving the wire so it cuts across the lines of a magnetic field
What is a magnetic field?
A magnetic field is a region where magnets such as iron and steel plus wires carrying current experience a force acting upon them
How does a dynamo work?
Cog wheel at the top is positioned so it touches one of the wheels as wheel moves round it turns the cog which is attached to the magnet this creates an AC current to power the light
What are the advantages of a dynamo?
No batteries so they wont run out
Renewable so doesn’t require electrical energy
What are the disadvantages of a dynamo?
Have to pedal
Not instant
What does flemings left hand rule tell us?
Which way the force acts
How do you change the direction of a force?
Reverse magnetic current or change magnetic field
How do you increase the size of a force?
Increase current and magnet strength
- size depends on the angle between the wire and field lines
Its at its greatest when its perpendicular to the field lines
Why do transformers only work on AC?
AC changes the direction of the magnetic field consistently and to induce a secondary coil there needs to be a changing magnetic field
How does a transformer work?
The current flows through the primary coil this creates a magnetic field, the current alternates so the magnetic field in the iron core is consistently changing. The rapidly changing magnetic field is felt by the secondary coil and the changing field induces an alternating PD across the secondary coil
What is the difference between switch mode and and normal transformer?
Lighter
Higher frequency
More efficient as it has a lower power supply and doesn’t have a load applied
What is a switch mode transformer used for?
Mobile phone chargers
Laptop chargers
How do you speed up electric motors?
More current
Increase strength of magnetic field
What does a spindle do?
Rotates coil
One force acts up the other acts down
What does a split ring commutator do?
Swaps contact every half turn to keep motor rotating in same direction
How can the direction of the motor be reversed?
Swapping polarity of DC supply
Swapping magnetic poles over
Why is an electromagnet useful?
Its useful as you can switch the current off and on and therefore turn the magnet on and off
How do you induce a magnet?
Moving a magnet in a coil wire
Turning a magnet end to end in a coil wire
How do you reverse current in electromagnetic induction?
Move magnet in opposite direction
What is the motor effect?
The force experienced by a current carrying wire in a magnetic field
How do you increase the size of induced current?
Increase the speed at which the coil rotates
Increase strength of magnetic field
Increase number of turns in the coil and increase total area of the coil
How does an electric motor work?
- Electric motor is turned on
- Current flows through the coil
- Flowing electron create a magnetic field
- The magnetic field of wire and magnet interact
- Equal and opposite forces experienced on each side
- Coil rotates half turns
- Momentum of coil pushes beyond half turn
- Split ring commutator ensures current remains on the same side
- Carbon brushes stop tangling
- Coil rotates another half turn and so on until it is switched off
Why does it have a iron core?
The iron core is purely for transferring the changing magnetic field from the primary coil to the secondary coil
- no electricity flows around the coil
