Electromagnetism Flashcards
What do the arrows do in a magnetic field?
Point away from north.
Do not cross.
Must have direction.
Continuous.
The closer the lines, the stronger the force.
What are examples of magnetic materials?
Iron,cobalt,steel,nickel.
Fletchings left hand rule
First finger- field
Thumb- thrust or force.
Second- direction of conventional current.
Which way does a magnetic field travel?
North to south
How could you change the direction of the force?
Change the direction of the magnetic field.
Change the direction of the current
How could you increase the size of the force?
Increase the size of the current.
Increase the strength of the magnetic field.
Increase the length of the wire in the field.
What could be done to make a motor turn faster?
Increase current.
Add more turns.
Increase the magnetic flux density.
How could you create a larger current?
Stronger magnetic field.
More turns on the coil.
Move the magnet or wire faster.
What is electromagnetic induction?
To induce a voltage and cause current to flow in a wire you need to have a changing magnetic field beside a wire
Coil 1 is switched on
The ammeter at coil 2 deflects momentarily then returns to zero
Coil 1 and 2 stationary
Nothing will happen.
No deflection in ammeter.
Coil 1 moved
Ammeter deflects and then returns to zero
Coil 2 moved
Same as coil 1 moved
Coil 1 switching off
Deflection in coil 2 (opposite direction to coil 1) then back to zero
What is direct current? D.C
Flows around the circuit in only one direction and it keeps the same steady value the whole time.
What is alternating current? A.C
Flows around a circuit in continually changing directions.
+- 325
50 cycles per second- 50hz
How can the size of a current be increased?
Increase the magnets power-magnetic flux density
Increase the number of turns of wire in the field.
Increase the speed that it’s turning at-angular velocity
Increase the coil length
What is a transformer?
Is a device that allows for the sizes of voltages to be changed.
It consists of two wire coils with a common soft iron core as shown below.
What is the formula for transformers?
Np/Ns = Vp/Vs
Where are transformers used?
Power station.
Transmission lines.
Before electricity enters our homes.
