Two horizontal metal rods, and , of different materials are resting on a frictionless table. Initially they are at rest in position 1.

Both rods are then connected to a battery using wires. After the switch is turned on, currents of different magnitude flow in each rod. The rods move to position 2 after time, . In position 2, has a larger displacement than from position 1. The masses of the wires are negligible.
 

1. Position 1 is reproduced below. Draw wires to show how the battery must be connected to the ends of the two rods in order for the magnitude of the current in each rod to be different, and for position 2 to be reached. No components, other than the wires, are required.   (2 marks)
    
    
   

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2. When the switch is turned on, the current in rod is greater than the current in rod .
3. Consider this statement.
4.     Position 2 results from the larger current in rod , causing a larger force to act on rod .
5. Evaluate this statement with reference to relevant physics principles.   (4 marks)
   

In a thought experiment, two identical parallel aluminium rods, and , are carrying electric currents of equal magnitude. Rod rests on a table. Rod remains stationary, vertically above , as a result of the magnetic interaction. The masses of the connecting wires are negligible.
 

Which statement must be correct if rod is stationary?

1. The magnetic force acting on is upward.
2. The currents through and are in the same direction.
3. The force the table exerts on is equal and opposite to the total weight of and .
4. The force the table exerts on is equal and opposite to the force of gravity acting on .

Two parallel conducting rods are connected by a wire as shown and carry current . They are separated by distance and repel each other with a force .
 

Which graph best shows how the current would need to be varied with distance to keep the force constant?
  

A student performed an experiment using two identical, current-carrying metal rods connected to a power supply. Rod was placed at different distances from Rod , and the measurements on the electronic balance were recorded.
 

What is the dependent variable in this experiment?

1. The current in
2. The length of the rods
3. The mass recorded on the balance
4. The distance between the two rods

, and are straight, current-carrying conductors. They all carry currents of the same magnitude . Conductors and are fixed in place. The magnitude of the force between conductors and is newtons.
 

What is the net force on conductor when it is in the position shown?

1. newtons to the left
2. newtons to the right
3. newtons to the left
4. newtons to the right

An AC supply is connected to a light bulb by two long parallel conductors as shown.
 

Which graph shows the variation over time of the magnetic force between the two conductors?
 

Three parallel wires , and all carry electric currents. A force of attraction is produced between and . There is zero net force on .
 

What is the magnitude and direction of the current in ?   (3 marks)

Two wires separated by a distance, , carry equal electric currents producing a magnetic force between them.
  

The separation between the wires is increased to and the current in each wire is doubled.

What happens to the magnetic force between the wires, compared to the original force?

1. It does not change.
2. It increases by a factor of 4 .
3. It decreases by a factor of 4 .
4. It decreases by a factor of 8 .

Two parallel wires, and , each carry a current .
 

The magnitude and direction of the force on wire are represented by the vector .

The current in wire is then doubled and its direction is reversed. The current in wire remains unchanged.

Which vector arrow represents the force on wire after the change to the current in wire ?
 

Two long, parallel conductors and are connected to a light bulb and an AC power supply. The conductors are suspended horizontally from fixed points using sensitive spring balances. is positioned directly below .
 

Which statement correctly compares the forces measured by the spring balances?

1. The forces measured on and will always be equal.
2. The force measured on will be greater than or equal to that on .
3. The force measured on will be greater than or equal to that on .
4. There will be a continuous reversal of which measured force is greater.