Magnetic Fields Due to Currents (Cambridge (CIE) A Level Physics): Flashcards
Exam code: 9702
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Describe the shape and strength of the magnetic field around a long, straight current-carrying wire.
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Cards in this collection (15)
Describe the shape and strength of the magnetic field around a long, straight current-carrying wire.
The field lines form concentric circles centred on the wire. They are closer together (stronger field) near the wire and further apart (weaker field) with increasing distance.
State the right-hand grip rule for finding the direction of the magnetic field around a straight wire.
Point the right-hand thumb in the direction of the current and curl the fingers onto the palm; the curled fingers show the direction of the magnetic field.
How is the right-hand grip rule applied to find the poles of a solenoid?
Curl the fingers in the direction of the current flow around the coil; the thumb then points in the direction of the field inside the coil, towards the north pole.
Describe the shape of the magnetic field produced by a solenoid.
It is similar to that of a bar magnet: field lines emerge from the north pole and return to the south pole.
How is the magnetic field of a flat circular coil related to that of a solenoid?
A flat circular coil is equivalent to one turn of a solenoid; combining the fields of many individual circular coils produces the field of a solenoid.
State two ways the magnetic field strength of a solenoid can be increased.
Adding a ferrous (iron) core
Adding more turns to the coil
The direction of current used in the right-hand grip rule is the .......... current, not the direction of electron flow.
The direction of current used in the right-hand grip rule is the conventional current, not the direction of electron flow.
True or False?
Reversing the direction of the current in a wire has no effect on the direction of its magnetic field.
False.
Reversing the current reverses the direction of the magnetic field.
What produces a magnetic field around a current-carrying conductor, and what determines its direction?
A current-carrying conductor produces a magnetic field around it. The direction of the field depends on the direction of the current, and is determined by the right-hand grip rule.
What happens to two parallel current-carrying conductors when their currents are in the same direction?
The magnetic field lines between the conductors cancel out, so the conductors attract each other.
What happens to two parallel current-carrying conductors when their currents are in opposite directions?
The magnetic field lines between the conductors push each other apart, so the conductors repel each other.
True or False?
The force between two attracting current-carrying conductors acts away from each other.
False.
When conductors attract, the magnetic force on each acts towards the other conductor; forces act away from each other only when the conductors repel.
What two factors determine the magnitude of the force between two parallel current-carrying conductors?
The amount of current in each conductor
The length of the wire
According to Newton's third law, how do the magnetic forces on two interacting current-carrying conductors compare?
The force on one conductor is equal but opposite in direction to the force on the other conductor.
If the currents in two parallel conductors flow in the .......... direction, the magnetic field lines between them cancel out and the conductors attract.
If the currents in two parallel conductors flow in the same direction, the magnetic field lines between them cancel out and the conductors attract.
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