# Physics

• Created by: Amy-C
• Created on: 11-05-18 14:34
State an equation that links current, charge and time, with units for each
Charge (C) = Current (A) x Time (s)
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What is meant by potential difference and resistance in a circuit?
Potential difference (or voltage) is the driving force that pushes the charge round. Resistance is anything in the circuit which slows the flow down
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What is the equation that links potential difference, current and resistance?
Potential difference = Current x Resistance
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What is an ohmic conductor?
The resistance of ohmic conductors (e.g. a wire or a resistor) doesn't change with the current. At a constant temperature, the current flowing through the ohmic conductor is directly proportional to the potential difference across it
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Name one linear component and one non-linear component
Linear component: ohmic conductor / Non-linear components: filament lamp
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Explain how the resistance of an LDR varies with light intensity
In bright light, the resistance falls. In darkness, the resistance is highest
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What happens to the resistance of a thermistor as it gets colder?
In cool conditions, the resistance goes up. In hot conditions, the resistance drops
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True or False? Potential difference is shared between components in series circuit
TRUE
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True or False? The current is constant in a series circuit
TRUE
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True or False? The potential difference across each component connected in parallel is different
FALSE
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True or False? Mains supply electricity is an alternating current
TRUE
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What is the potential difference and the frequency of the UK mains supply?
230 V / 50 Hz
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Name and give the colours of the three wires in a three-core cable
Neutral wire - Blue / Live wire - Brown / Earth wire - Green and Yellow
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Give the potential differences for the three wires in a three-core mains cable
Neutral - 0 V / Earth - 0 V / Live - 230 V
14 of 23
Explain why touching a live wire is dangerous
A large potential difference is produced across your body and a current flows through you. This causes a large electric shock which could injure or even kill you
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State three equations that can be used to calculate electrical power
Energy transferred = Power x Time / Energy transferred = Charge flow x Potential difference / Power = Potential difference x Current
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What is the power rating of an appliance?
They're labelled with the maximum safe power that they can operate at. You can usually take this to be their maximum operating power
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Explain why electricity is transferred by the national grid at a high pd but low current
To transmit the huge amount of power needed, you need either a high pd or current. It’s much cheaper to boost the pd up really high and keep the current relatively low. Increasing the pd decreases the current, which decreases energy loss.
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What are the functions of step-up and step-down transformers?
The potential difference is increased using a step-up transformer. It’s then reduced again for domestic use using a step-down transformer
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How does rubbing of materials cause static electricity to build up? (Friction)
When certain insulating materials are rubbed together, negatively charged electrons will be scraped off one and dumped on the other. This will leave the materials electrically charged, with a positive static charge on one and negative on the other
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True or False? Two positive charges attract each other
FALSE
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In which direction do the arrows on electric field lines point?
They go from positive to negative
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Using the concept of electric fields, explain how a build up of static electricity can cause a spark
Sparks are caused when there is high pd between a charged object and earth. A strong electric field causes electrons in air particles to be removed (ionisation). Air is normally an insulator but when ionised it’s more conductive. A current flows.
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## Other cards in this set

### Card 2

#### Front

What is meant by potential difference and resistance in a circuit?

#### Back

Potential difference (or voltage) is the driving force that pushes the charge round. Resistance is anything in the circuit which slows the flow down

### Card 3

#### Front

What is the equation that links potential difference, current and resistance?

### Card 4

#### Front

What is an ohmic conductor?

### Card 5

#### Front

Name one linear component and one non-linear component