Current Electricity

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  • Created by: Rachel
  • Created on: 10-10-12 20:16
What happenes when insulating materials are rubbed together?
They become charged.
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What is transferred when objects become charged?
Electrons.
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What happens when charges are brought together?
Like charges repel,unlike charges attract.
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What is the difference between a battery and a cell?
A battery consists of two or more cells conected together.
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What determines the size of an electric current?
The rate of flow of charge.
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How do we calculate electric current?
Charge flow divided by time taken.
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What do we mean by potential difference?
Work done or energy transferred (in joules) divided by charge (in coulombs).
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What is resistance and what is its unit?
Resistance (in ohms)=potential difference(volts) divided by current (amps).
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What is Ohm's law?
Ohm's law states that the current through a resistor at a constant temperature is directly proportional to the potentil difference across the resistor.
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What happens if you reverse the current in a resistor?
Reversing the current thorugh a component reverses the pd across it.
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what happens to the resistance of a filament bulb as its temperature increases?
Resistance increases with increase of the filament temperature.
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How does the current through a diode depend on the potential difference across it?
"Forward" resistance low, "Reverse" Resistance high.
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What happens to the resistance of a thermistor as its temperature increases and of an LDR as the light level increases?
Thermistor: Resistance decreases as its temperature increases.LDR:
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How do we calculate current through a resistor in a parallel curcuit?
Current=potential difference divided by reistance.
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What is an electric current?
An ecectric current is a flow of charge/electrons.
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How do we calculate the flow of electric charge form the current?
Charge (coulombs)=current (amps) x time (seconds).
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What energy transfers take place when charge flows through a resistor?
Energy transfered into the resistor makes it hot.
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What do we use a fuse for?
A fuse contains a thin wire that heats up, melts, and cuts off the current if the current is to large.
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What is a curcuit breaker?
Its is an elctromagneitc swith that opens and cuts off the current if too much current passes thorugh a curcuit breaker.
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What can we say about the currents in the components in a parallel curcuit?
-The total current is the sum of the currents through the separate componets. -The bigger the resistance of a component, the smaller the current is.
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How can we calculate current througha resistor in a parallel curcuit?
Current= potential difference (volts) divided by resistance (ohms).
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What can we say about the current and potential difference for componets in a series curcuit?
-The current is the same in each component.-Adding the potential difference gives the total potential difference.
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How can we find the total resistance of resistors in series?
Ading the resistance gives the total resistance of resistors in series.
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What can we say about the potential difference of several cells in series?
For clees in series, acting in the same direction, the total potential difference is the sum of their individual potential differences.
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What happens to the potential difference across a resistor if the current is reduced?
The potential difference decreases.
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What happens to the potential difference across a component when you reverse the current through it?
It reverses too.
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Other cards in this set

Card 2

Front

What is transferred when objects become charged?

Back

Electrons.

Card 3

Front

What happens when charges are brought together?

Back

Preview of the front of card 3

Card 4

Front

What is the difference between a battery and a cell?

Back

Preview of the front of card 4

Card 5

Front

What determines the size of an electric current?

Back

Preview of the front of card 5
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