# Domestic electricity for SQA National 5 Physics

1. Direct potential difference
2. Alternating potential difference

Direct current is electric current that always flows in one direction. Direct current can be described as a constant flow of electrons from an area of high density of electrons to an area of low density. Direct current in a circuit causes a constant voltage circuit. Direct current is used in appliances and devices that use batteries as a power supply.

Alternating current is electric current that periodically changes direction. It is the type of current used by most power distribution systems and generated by most power plants. Alternating current holds the advantage over direct current that it can be generated for cheaper and it suffers less energy losses when transmitted over long distances.

# 1

Explain the direction of alternating current.

The direction of alternating current will periodically change.

# 2

Explain what direct current means for the voltage in a circuit.

Direct current in a circuit causes a steady voltage.

# 3

State which of the graphs represents direct current and alternating current.

Graph A represents alternating current, since the voltage varies. Graph B represents direct current, since the voltage is constant.

# 4

A voltage-time graph has been given for a circuit. State the type of current flowing through the circuit.

The circuit has a steady voltage, which means that the current in it is direct current.

# 5

State the uses of alternating current.

Alternating current is the type of current used by most power distribution systems and generated by most power plants.

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