2Ampere’s experiments (1)

Interaction between the conductor and current, Ampere's experiments

1

To explain the physical meaning of magnetic induction vector based on problem solving and modern technological advances (magnetic levitation train, etc.)

2

A current-carrying wire is surrounded by a magnetic field. This magnetic field interact with an external magnetic field, giving rise to a force on the conductor.
The magnets create a fairly uniform magnetic field.
As soon as the current in the copper rod is switched on, the rod starts to roll, showing that a force is acting on it.
Why?

The external magnetic field of the magnets
The magnetic field of the current-carrying conductor
The combined fields of the current-carrying conductor and the magnets

The production of this force is known as the motor effect, that is why the rod starts to roll, showing that a force is acting on it.

1. First, arrange the connections so the current is passing down both strips of foil. Set the power supply to 1 V. Switch on and describe what happens.
2. Increase the power supply to
2V. What happens now?
3. Arrange the connections so that
the current is passing up both
strips of foil. What happens?
4. Finally arrange the connections so the current is passing up one foil and down the other. What is the result?

(a) Two parallel
conductors carrying currents I1 and I2
(b) Magnetic field B1 produced by I1 (Field produced by I2 is not shown.)
B1 points into page at position of I2.

(a) Parallel currents in
the same direction exert an attractive
force on each other.
(b) Antiparallel
currents (in opposite directions) exert
a repulsive force on each other.

a shows two
unlike (anti-parallel) currents, one flowing into the page,
the other flowing out of the page. Their magnetic fields
circle round. The diagram shows the resultant field, and the repulsive
forces on the two wires.

b shows the same idea, but for two like
(parallel) currents. In the space between the two wires, the magnetic fields cancel out. The wires are pushed together.

Which one of these labelled diagrams correctly shows
the field between two conductors carrying current in
opposite directions?

2. The diagram below shows the forces on two parallel conductors when they carry currents of the same magnitude in opposite directions perpendicular to the page.

3. A student places a current-carrying conductor between two magnets. The current flows
upwards out of the page. In which direction will the conductor experience a force?

4. Three parallel conductors P, Q and R carry identical currents. The three conductors
experience resultant magnetic forces in the directions indicated in the sketch below:

5. A conventional current flowing in conductor X, in a direction out of the surface of the
paper at a right angle to the magnetic field, is shown in the diagram below.

1 – B
2 – C
3 – A
4 – C
5 – A

What has been learned
What remained unclear
What is necessary to work on