Electric current
Transcript of Electric current
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The Voltage of a Cell.The ability of a cell to drive a current is measured
by its voltage.
The volt symbol “V”.
When cells are arranged in series with the positive
terminal of one cell connected to the negative
terminal of the next cell, it can be calculated by
adding their voltages.
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The potential difference or voltage between two
points in a circuit is measured by a voltmeter.
The voltmeter is connected into a circuit with its positive terminal connected to a wire that leads towards the positive terminal of the cell.
Measuring Voltage.
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In an ammeter, the wires are attached to either side of the part of the circuit being tested.
It is arranged in parallel with this part of the circuit.
Measuring Voltage.
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Ohm’s Law
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Resistance The material through which a current flows offers
some resistance to the moving electrons.
High resistance
Low resistance
Small current with an
applied voltage
Large current with the
same voltage
an
d
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The wires connecting the components in a
circuit have a low resistance while wires in
filaments of the lamps has high resistance.
When they connect in series their resistance
combine the same way as the voltages of
the cells in series – They add.
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LAMPS AND CURRENT SIZE
The size of the current flowing can be
estimated by looking at the brightness of the
lamps.
The lamp will shine brighter with more power
and it will shine less when there is less power.
The lamp also shares it’s power with other
components in the circuit.
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The ammeter reading varies in the following way. At points A and D the
readings are the same. At points B and C, if the lamps are identical the
readings will be the same and exactly half the readings at A and D. so if A
and D are 6.0 amps the readings at B and C will be 3.0 amps.
A D
B
C
The total of the readings of the ammeters at B and C is
always the same as the reading at A and D even if the
bulbs are not identical. For example: if the reading at A and
D is 5.0 amps and the reading at B is 3.0 amps then the
reading at C will be 2.0 amps.
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LIGHT-DEPENDENT
RESISTOR
A light-dependent resistor (LDR) is made from 2 piece of
metal which are jointed together by a semiconductor.
Semiconductor is a material that has just a few
electrons which can move freely. When the LDR receives
light energy, more electrons are released in the
semiconductor, and the resistance of the LDR becomes
lower. When the amount of light shining on it reduced,
fewer electrons are released and the resistance
increases.
This is the
symbol for
LDR
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Normal Bright
Dim
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• Current can flow only in one direction.
• Used to control the direction of the flow of
a current through complicated circuits
(components in series and parallel).
• Have a band marked at one end.
• The symbol should be drawn with the
straight line facing the negative terminal of
the source of the current.
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LED
• An LED is a semiconductor diode,
allowing a current to flow in only one
direction and it produces light.
• It can emit red, yellow and green light.
• In electronic circuits an LED performs the
same task more efficiently.
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PRESENTED BY :
MASON
TASYA
PAWITRA
WILL
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Thank you for listening and
paying attention