Electricity Flashcards
(22 cards)
What does insulation, earthing, fuses and breakers do?
Protects the device or user in domestic appliances from being electrocuted
What does current in a resistor result in?
The transfer of energy and an increase in temperature. This can be useful for a kettle or microwave
What is the formula for power?
Current * voltage
What is the formula for energy transferred?
current * voltage * time
What is mains supply (a.c.)?
The current is constantly changing direction
What is battery supply (d.c.)?
The current will always flow in the same direction
What does current in a series circuit depend on?
The applied voltage and the number of other components in that series circuit.
How does a light dependent resistor change resistance?
In bright light the resistance falls and in darkness the resistance increases
How does a thermistor change resistance?
In hot conditions the resistance drops and in cool conditions the resistance goes up
What can indicate presence of current in a circuit?
Lamps and LEDs
What is the formula for voltage?
current * resistance
What is the definition for current?
The rate the charge flows
What is the formula for charge?
Current * time
In parallel circuits how do you find the current?
You add all the components currents together
In parallel circuits how do you find voltage?
Voltage is the same across all branches
What is the definition for voltage?
Energy transferred per unit charge passed
What is the definition for a volt?
Joule per coulomb
What is the formula for energy transferred?
Charge * voltage
Why is fuelling aircraft and tankers dangerous?
1) As the vehicle is fuelled static is built up
2) This can lead to a spark which will result in an explosion
How do inkjet printers work?
1) Drops of ink are forced out of a nozzle making them electrically charged
2) The droplets are deflected as they pass between the two metal plates
3) The droplets are attracted to the plate of the opposite charge and repelled from the plate with the same charge
4) The size and direction of the voltage across each plate changes so each droplet is deflected to hit a different place on the paper
How do photocopiers work?
1) The image plate is positively charged. An image of what your copying is projected
2) Whit bits of what your copying make light fall on the plate and the charge leaks away in those places
3) The charged bits attract negatively charged black powder which is transferred onto positively charged paper
4) The paper is heated so the powder sticks
