Electromagnets + Motor Effect Flashcards
When can a magnetic field be created?
When a current flows through a conducting wire a magnetic field will be produced around the wire
What does the strength of a magnetic field depend on in terms of the current
The size of the current
If the direction of the current is changed, what also changes?
The direction of the magnetic field
What is the Right Hand Grip rule and how can we use it?
The right hand grip rule is used to work out the direction of the magnetic field produced by a wire.
We place our right hand so that the thumb (thumbs up position) is pointing in the direction of the conventional current. The fingers will be pointing in the direction of the magnetic field and the thumb will be pointing NORTH.
How to increase the strength of the magnetic field in terms of the wire and what is it called?
We can coil the wire. It is called a solenoid. When we turn on the current we got a strong and uniform magnetic field inside the solenoid.
What are the 3 ways we can increase the strength of the magnetic field produced by a solenoid?
- Increasing the current
- Increasing the number of “turns” in the coil
- Placing a piece of iron inside the solenoid
Electromagnet definition
A solenoid with an iron core
The Motor Effect
As we know, a magnetic field is produced when a current moves through a wire. The motor effect is when the wire in another magnetic field. The 2 magnetic fields interact with each other and create a force.
Magnetic Flux Density Definition
The strength of a magnetic field
What 3 factors affect the size of the force in the Motor Effect?
- Magnetic flux density/strength of the magnetic field
- Current
- Length
What is Fleming’s left hand rule and what is it used for?
Fleming’s left hand rule is used to determine the direction of the force, magnetic field or current. Point your index finger in the direction of the magnetic field (from North to South), point your middle finger in the direction of the conventional current. Point your thumb in the direction of the motion/force.
How can we not experience a field in the motor effect?
If the conductor/wire is parallel to the magnetic field, a force will not be experienced.
What happens if there is a loop of wire that is carrying a current which is running in opposite directions on the sides of the loop and then this loop is placed in another magnetic field?
The loop will experience opposite forces on both sides, which we will be able to see using Left Hand Fleming’s Rule. As a result of this, the loop will rotate but once the loop is at 90 degrees, it will stop rotating.
How can we solve the problem of the loop not rotating past 90 degrees?
We can use something called a split-ring commutator, which is a split metal ring which are connected to electric brushes. Once the loop hits 90 degrees, the current will be broken for a split second but the wire will keep turning due to momentum. This process will continue allowing the motor/loop to keep rotating in the same direction.
