Electric Motors

Question 1

what is the basis of the motor effect

Answer 1

a wire carrying a current, held in a magnetic field, will experience a force

Question 2

what would the orientation of the wire with respects to the magnetic field be if you wanted to maximise this effect

Answer 2

the wire would need to be perpendicular to the field

Question 3

what would the direction of the force therefore be in this case

Answer 3

• perpendicular to both the wire and the field

- in the third dimension

Question 4

what is the rule that visualises this concept

Answer 4

flemings left hand rule

Question 5

what do each of the fingers in flemings left hand rule stand for

Answer 5

• the thumb is the direction of the force / motion
• the index finger is the direction of the field
• the middle finger is the direction of the conventional current

Question 6

what is the simple thought process to remember this

Answer 6

• first finger field
• second finger (CONVENTIONAL) current
• motion showing thumb

Question 7

a wire is place in between a north pole on the left and a south pole on the right. the wire has its terminals placed such that the current would be flowing from the top of the wire to the bottom in the horizontal plane, aka towards you (the part that is in the magnetic field). first of all, where would your index finger be pointing (i assume you haven’t forgotten the finger setup for the rule)

Answer 7

• magnetic field lines go from the north to south pole

- so the first finger field would point to the right

Question 8

where would you middle finger be pointing

Answer 8

• conventional current would be flowing in the opposite direction to actual current
• so the second finger current would point from the bottom to the top in the horizontal plane
• in other words, away from you

Question 9

therefore, which direction would the wire move in

Answer 9

• in the form of flemings left hand rule, your motion thumb would be pointing downwards
• so the wire would move downwards

Question 10

for the sake of understanding, what does conventional current even mean

Answer 10

• its not just the opposite direction that current would actually be flowing in the circuit
• its the direction that positive charge in the circuit would be flowing
• as the effect of -ve charge flowing in one direction is the ‘flow’ of +ve in the other

Question 11

what would the force on a wire be if the flow of current was parallel to the magnetic field

Answer 11

0

Question 12

how does a motor with a coil of wire cause the coil to rotate

Answer 12

• the coil of wire carrying a current is placed in a magnetic field
• because the current on opposite ends of the coils would be travelling in opposite directions
• the force exerted on opposite ends of the coils would be in the opposite direction to each other
• creating a turning force which rotates the coil around

Question 13

what is the effect of the rotation of the coil

Answer 13

• the coil is the motor in this setup
• if its free to spin continuously, it would generate kinetic energy
• which generates electrical energy that powers whatever its meant to power