Use the power equation (for transformers with100% efficiency):
potential difference across primary coil (volt, V) × current in primary coil (ampere, A) = potential difference across secondary coil (volt, V) × current in secondary coil (ampere, A)
Use the power equation (for transformers with100% efficiency):
potential difference across primary coil (volt, V) × current in primary coil (ampere, A) = potential difference across secondary coil (volt, V) × current in secondary coil (ampere, A)
Explain the advantages of power transmission in high-voltage cables, using the equations in 10.29, 10.31, 13.7P and 13.10
**Explain how to produce an electric current by the relative movement of a magnet and a conductor
a) on a small scale in the laboratory b) in the large-scale generation of electrical energy**
Recall the factors that affect the size and direction of an induced potential difference, and describe how the magnetic field produced opposes the original change
Explain how electromagnetic induction is used in alternators to generate current which alternates in direction (a.c.) and in dynamos to generate direct current (d.c.)
Explain the action of the microphone in converting the pressure variations in sound waves into variations in current in electrical circuits, and the reverse effect as used in loudspeakers and headphones
Explain how an alternating current in one circuit can induce a current in another circuit in a transformer
Recall that a transformer can change the size of an alternating voltage
Use the turns ratio equation for transformers to calculate either the missing voltage or the missing number of turns:
Explain why, in the national grid, electrical energy is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic uses as it improves the efficiency by reducing heat loss in transmission lines
Explain where and why step-up and step-down transformers are used in the transmission of electricity in the national grid