Exam Questions Flashcards
A student rubs a piece of plastic with a cloth. The gives the plastic a negative charge.
Explain why the plastic is charged by the rubbing.
Electrons are removed by friction and transferred to the plastic
Why do, when fuel tanks are being filled, the aircraft, fuel pipes and tanker need to be connected to a metal wire to the ground?
It reduces the chance of a spark
The charges flow through the metal wire
To the ground / earth
Preventing a build up of charge
A student rubs a piece of plastic with a cloth. The gives the plastic a negative charge.
What is the charge of the cloth
It is opposite to the charge on the plastic (positive charge therefore)
It is equal to the charge on the plastic
When the light meter has been used for a long time, the meter reading becomes incorrect.
Suggest what has happened.
The battery voltage has decreased so there is less current
Can diode conduct in only one direction or in 2?
Diodes can only conduct in ONE direction
Why are diodes often included in circuits?
To make sure the meter connections are the right way around
The current in a heater element in a flow of…
Electrons
12V is the same as?
12 J/C
Give an example of a device where the heating of an electric current is a disadvantage.
Light bulb / Overheating computer
How can the potential difference across the heater be measured in?
Volts
Joules pee coulomb
Why does the resistor become hot?
Because of the electrons colliding in the atoms
