Electricity Flashcards
What is ohm’s law?
voltage = current x resistance
If we increase the resistance of a component, what happens to the current flowing through it?
It decreases.
What is a series circuit?
A circuit with all components connected one after another, in one path.
What is a parallel circuit?
A circuit with the components connected in different branches, there is more than one path around the circuit.
What is a battery?
Two or more cells
What does an ammeter measure?
Current in Amps (A). They are connected in series.
What does a voltmeter measure?
Potential Difference or Voltage in Volts (V). They are always connected in parallel.
What colour is the live wire?
Brown
What colour is the earth wire?
Green and yellow striped
What colour is the neutral wire?
Blue
Which wire is connected to the fuse?
Live (brown one)
Which side of the plug does the live wire go?
Right (bRown - Right)
Which side of the plug does the neutral wire go?
Left (bLue - Left)
What material (and why??) is the plug casing made of?
Plastic - because it is an insulator
What material (and why??) is the inside of the wire made of?
Metal (copper) because it is a conductor
What is the voltage of UK mains?
230V
What is the frequency of UK mains?
50Hz
What does the horizontal (x-axis) show on an oscilliscope trace?
Time
What does the vertical (y-axis) show on an oscilliscope trace?
Voltage
What is inside a fuse?
A thin wire which melts if the current is too high
Why do some appliances not need an earth wire?
They are double insulated
The resistance in a thermistor increases as?..
…temperature decreases.
The resistance in an LDR increaes as?
?light intensity decreases.
To find the total resistance of two resistors in series we?.
?add them.
What does a DC supply look like on an oscilliscope trace?
A straight horizontal line
What is this component and what does it do?
It is an ammeter, it measures current in Amps (A)
For what is this the symbol?
What does the component do?
It is a battery. A battery is more than one cell - it delivers energy to the circuit.
The total voltage of the battery is the sum of all the cells
What is this the symbol for and what does it do?
A cell. It delivers energy to the circuit.
What component is this the symbol for and what does it do?
Diode
It allows the current to flow in one direction only (the direction the arrow is pointing).
What component is this the symbol for and what does it do?
A fuse
It melts and breaks the circuit if too large a current flows through it.
What component is this the symbol for and what does it do?
A lamp.
It converts electrical energy to light (useful) and heat (wasted).
What component is this the symbol for and what does it do?
A Light Dependent Resistor (LDR)
Its resistance alters depending upon the brightness of the light falling on it. The brighter the light, the lower the resistance.
What component is this the symbol for and what does it do?
A Light Emitting Diode (LED)
Like a diode, it will only let current flow in one direction (the direction of the arrow). It indicated that a current is flowing with a small light - e.g. a ‘power on’ light
What component is this the symbol for and what does it do?
A resistor
It controls the amount of current in a circuit (for a fixed voltage).
What component is this the symbol for and what does it do?
A Thermistor
It is a resistor that changes resistance depending on temperature. High temperatures mean a lower resistance.
What component is this the symbol for and what does it do?
A Variable resistor.
These are resistors that can change their resistance. They can be used to control a current in a circuit e.g. a dimmer switch or volume control
What component is this the symbol for and what does it do?
A Voltmeter
This measures the Potential Difference (P.d. or Voltage) between two points in a circuit. They are connected in parallel.
This is the current voltage graph for a ….
Filament lamp.
As it’s temperature increases, the resistance increases because the electrons find it more difficuklt to move past atoms that are vibrating more rapidly.
This is a current voltage graph for a …..
Straight wire at constant temperature.
The voltage is proportional to the current
This is a current voltage graph for a …..
Diode
Current can flow in one direction only
What is current?
Current is the flow of charge (electrons) around a circuit.
It alwas flows from the positive (long) side of a cell or battery to negative (short)
What is the symbol for current
I
Two insulators are rubbed together and create static electricity. How does this happen.
The friction between the two insulators rubs electrons off one onto the other
Two insulators are rubbed together and become charged. Explain why one is negative and one positive
Negative electrons have moved. The insulator that is negative has gained electrons. The insulator that is positive hads lost electrons.
Similar charges ….
repel.
Opposite charges ….
attract.
A charged object will discharge if …
it is Earthed
An ‘Earthed’ object has..
a conducting (metal) path to the ground.
