Physics - Electric circuits Flashcards
(23 cards)
Draw the symbol for a cell
(which is the same as a battery in a circuit)
Draw the symbol for a switch
draw it OPEN, not CLOSED!
Draw the symbol for a LAMP
Draw the symbol for a VOLTMETER
Draw the symbol for an AMMETER
Draw the symbol for a RESISTOR
Draw the symbol for a VARIABLE RESISTOR
Draw the symbol for a FUSE
Draw the symbol for a LED
(Light Emitting Diode)
Draw the symbol for a THERMISTOR
and what does a thermistor do?
A thermistor is a resistor which changes it’s resistance depending upon the temperature
Draw the symbol for a LDR
(Light Dependent Resistor)
and what does it do?
An LDR is a resistor which changes it’s resistance depending upon how much light is shining on it.
Draw the symbol for a DIODE
Describe electrical CURRENT
The symbol ‘I’ is used for electrical current.
Current is the flow of electrons around an electrical circuit.
It is measured in amperes, symbol ‘A’
It is measured by an ammeter, which needs to be in series
What is VOLTAGE
Voltage is a measure of how much electrical energy a certain amount of electrons can transfer as they flow around a circuit.
The higher the voltage, the more electrical energy is supplied to the circuit.
Voltage is measured in Volts, symbol ‘V’
Measured by a voltmeter, connected in PARALLEL
Two bulbs - B1 and B2 - are connected together along with a battery (cell).
Describe how they are fastened together -
are they in series or in parallel?
And what happens if bulb B1 breaks?
B1 and B2 are connected in series
If bulb B1 breaks then bulb B2 will not work
Describe how bulbs B1, B2 and B3 are connected.
What happens to bulb B2 and B3 if bulb B1 breaks?
B1 and B2 are in series
B3 is in parallel to B1 & B2
If B1 breaks then B2 will not work but B3 will still work
What happens to
voltage (volts) and current (amps)
in a circuit where two bulbs are in series?
The voltage is split across both bulbs. So, in the picture, if the voltage from the battery is 6V, and the voltmeter V1 shows 3V, then the voltmeter V2 will also show 3V (3V+3V=6V)
The current through both bulbs in series is the same
What happens to
voltage (volts) and current (amps)
in a circuit where two bulbs are in parallel?
The current is split across B1 and B2
The voltage is the same through both bulbs
Give some uses of a variable resistor
A variable resistor (rheostat) is a resistor for which it is possible to alter/vary the resistance. This allows you to control the current in a circuit.
Examples:
- DIfferent heat settings on a hairdryer
- A dimmer switch on the lights in a room
- The volume control on a radio
Explain Ohms Law
It is the equation which links resistance, voltage and current.
…. so if you know two of the three, you can work out the third.
Define
electrical power
This is the rate (per second) of energy transfer
It is measured in watts
There is an equation to calculate it
Power = voltage (volts) x current (amps)
Give an example of how a light dependent resistor is used
The resistance changes according to the amount of light.
They can be used to automatically switch on street lights
Give an example of how a thermistor is used
The resistance changes according to the temperature.
They can be used to set off fire alarms if the temperature in a room goes too high
