Physics 5.16 - 5.18

Question 1

Explain how direct current motors work step by step

Answer 1

Direct current motors work by applying the motor effect which states that a current carrying wire will experience a force when in the presence of a magnetic field. The forces direction can be determined by flemmings left hand rule. We can connect both ends of the wire to a split ring commutator to ensure that the direction of the current swaps every half turn to avoid the wire spinning back and forth. Then we one connect contact on each side of the split ring commutator, one positive, one negative. These will allow us to drive current through the wire. Then we place the wire in between a magnet perpendicularly so that it experiences the full force of the magnetic field/flux. Once we connect the circuit to a power source, the wire will start spinning providing us with a working d.c motor

Question 2

What is the work of a split ring commutator

Answer 2

It swaps the direction of the positive and negative connections every half turn which results in changing directions of current

Question 3

What are the two types of generators?

Answer 3

Step up and step down generators

Question 4

Explain how generators are used step by step

Answer 4

Electricity is generated by the national grid which is then run through a step up generator. A step up generator is one that can transform a low voltage into a high voltage. Generators work by inducing an alternating voltage on the primary coil, which creates an alternating magnetic field on the coil which transfers to the iron core of the generator. The alternating magnetic field on the iron core will then induce a current on the secondary coil which usually has more or less turns than the primary coil. This in turn will produce a higher or lower voltage than the primary coil. For the national grid, the electricity is stepped up in order to minimize power loss while transporting the electricity across long distances, which is then stepped down to around 230v before it enters our homes

Question 5

State the two formulas used in transformer calculations

Answer 5

Vp/Vs = Np/Ns
VpIp = VsIs

V = Voltage
N = number of turns in coil
I = current
p = primary
s = secondary