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  • Created by: lina sama
  • Created on: 27-07-10 13:57

Current is measured in Amps (A) using an Ammeter

Voltage is measured in Volts (V) using a Voltmeter

Voltage = Current x Resistance

The resistance in a circuit can be increased by adding more components, such as resistors and lamps.

Circuit symbols

The diagram below shows the standard circuit symbols you need to know.

two horizontal lines with a gap where one line is at 45 degrees  (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_a.gif)

Open Switch

two horizontal lines with a join in the centre (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_b.gif)

Closed Switch

a circle with an 'x' inside, attached to a horizontal line either side (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_c.gif)

Lamp

two 't' shapes head to head, one with a thicker top (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_d.gif)

Cell

three t-shapes, the one on left flipped to the right, the two on the right flipped 90 degrees to the left. the two on the right side have a thicker "top". (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_e.gif)

Battery

a circle with a 'V' in the centre. two horizontal lines come out from either side of the circle. (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_f.gif)

Voltmeter

a rectangle lying flat with two horizontal lines coming out of its sides (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_g.gif)

Resistor

a rectangle lying flat with one horizontal line running through the centre of it and out of both sides (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_h.gif)

Fuse

a circle with an 'A' in the centre with two horizontal lines coming out of the sides of the circle (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_i.gif)

Ammeter

a rectangle lying flat with an arrow running through it at a 45 degree angle. two horizontal lines run out of the sides of the rectangle (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_j.gif)

Variable resistor

a rectangle lying flat with two horizontal lines running out either side of it. A 45 degree line runs through the rectangle which bends at the bottom to run parallel with the base of the rectangle (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_k.gif)

Thermistor

a rectangle lying flat with two horizontal lines running out of either side. a circle runs around the rectangle, and two arrows point downwards at the rectangle, from the top left. (http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect01_l.gif)

Light dependent resistor (LDR)

Two things are important for a circuit to work:

  • there must be a complete circuit
  • there must be no short circuits

A current flows when an electric charge moves around a circuit. No current can flow if the circuit is broken, for example, when a switch is open…

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