The Motor Effect

What is the motor effect

How does it work → process of how it is created?

definition: the magnetic force (F=BIL sinθ) a current carrying conductor in a magnetic field experience due to the interaction between the magnetic field created by the current and the existing magnetic field.

• Current = the flow of charge per unit of time  acts as the direction of motion (aka velocity) for the charges

process:

1. The current consists of moving charges that are perpendicular to the magnetic field.

2. Thus, each charge experiences a force F=qvBsin𝜃.

3. Hence, the entire conductor experiences a force in the magnetic field as the sum of these forces, and this is called the motor effect

Ampere’s Force Law

Applies to Parallel Current Carrying Conductors

• A current produces a magnetic field ∴ current carrying conductors experience a force when they interact with the magnetic fields of other current carrying conductors

• Current in same direction (in parallel) = opposite B fields = attract

• Current in opposite direction (in series) = like B fields = repel

Due to N3L, the forces on each of the wires are equal and opposite:

Parallel Current Carrying Conductors experiment

1. Two wires are connected to a current/one current and a magnet

2. Different currents are run through one of the wires/current wire is run infront or behind of the magnet

3. A balance is used to record the ‘mass’ of a rod/magnet

   1. This balance reading is not actually the mass of the rod, but the net force

4. For top wire

   1. Balance reading decrease = repulsive force that is making it move upwards (↓ Fnet)

   2. Balance reading increase = attractive force that is pulling it down (↑ Fnet)

5. For bottom wire

   1. Balance reading decrease = attractive force that is making it move upwards ((↓ Fnet)

   2. Balance reading increase = repulsive force that is pulling it down (↑ Fnet)

6. You graph the information

7. Find the gradient of the line and its significance: either F=BIL or or ampere’s force law

8. Insert the gradient into the equation and rearrange for unknown value

How to change the direction vs the magnitude of force (F=BIL)

Magnitude	direction
Increase θ to 90° = increase F Maximum force produced when θ=90°, i.e. the current is completely perpendicular to the magnetic force No force when current and magnetic field are parallel Increase magnitude of the current = increase F No current = no force Include more length of wire in the field = increase F Increase strength of the magnetic field = increase F	Reverse the direction of the current Reverse the magnetic field strength