P2 (physics)(book) Flashcards
What do opposites charges do ?
Opposite charges attract
What do like charges do ?
Like charges repel
How can static electricity be produced?
Can be produced by rubbing two insulators together
What is static electricity the build up of & why is it called static?
It is the build up of charge
It is called static because the charge cant move
What can conductors do?
They can conduct electricity
What cant insulators do?
They cannot conduct electricity
What are needed in order for current to flow?
Power source
Conducting material
Closed circuit
What is electric current?
The rate of flow of charge
What is current ?
It is how much of something in one second
the rate at which electrons flow past a point in a complete electrical circuit
What is charge measured in?
Coulomb
Define amps
Amps= coulombs per second
1A = 1 coulomb ÷ second
State the equation for charge
Charge = current x time
Q = I x t
What is voltage measured in?
Volts
What is an ammeter measured in?
Amps
What is resistance measured in?
Ohms , Ω
Write the equation to calculate the voltage?
V = I x R
What is current directly proportional to?
The voltage
If v doubles what happens to I ?
I doubles
If V halves what happens to I ?
I halves
In a parallel circuit what does the current do between branches?
The current is spilt between branches
What is the voltage like across each branch in a parallel circuit?
The voltage is the same across each branch
What is the I like in a series circuit?
I is the same everywhere in the circuit
What is the v like in a series circuit?
V of the cell / battery is shared between components
What is resistance caused by?
Resistance is caused by collisions between flowing electrons and positive metal ions (fixed , vibrating in place)
What happens to the current, if the resistance of a circuit increases?
Current decreases
What is ohms law?
A line goes through proportionally through the origin
Current (I) is directly proportional to v (voltage) as long as the temperature is constant
A positive ballon is rubbed on a negative jumper and becomes charged. Explain how this happens?
Electrons are transferred through friction
Describe and explain how increasing the length of a Wire affects its resistance
The longer the wire the longer the resistance
Resistance is caused by collisions between flowing electrons and positive metal ions
In a longer wire these collisions are more frequent
What does the filament bulb not obey?
Ohm’s law
As the potential difference increase what happens to the current in a filament bulb?
Current also increases
Higher voltage means higher what in a filament bulb
Higher resistance
What happens to the filament as more current flows & why is that?
The filament bulb gets hotter
Metal ions gain energy and vibrate faster causing more frequent collisions
Why is a variable resistor used?
To get a range of value for the voltage
Current flows from what to what?
Current flows from positive to negative
What does the component diode do?
It allows the current to flow in one direction
Define alternating current
The current changes direction continuously
What is the voltage of main electricity?
230V
What is the frequency of main electricity?
50Hz
What does the fuse prevent?
It prevents too much current going through it so it doesn’t overheat
When it does a wire inside the fuse melts so no current and flow
What is the function of an earth wire?
To carry charge away from a live casing
For safety: to avoid an electrical shock from a metal casing becoming charged
What is voltage?
Potential difference is how much joules are added to each coulomb of charge
State the equation for electrical work done
E = Q x V
Electrical work done = charge x potential difference
(J) = (c) x (v)
E=P x t
Define power
Rate of energy transfer
Define national grid
System of transformers and cables
What happens at the step up transformer?
Increases the voltage
Lowers the current
So the wire doesn’t overheat
So less energy is dissipated
What happens at the step down transformer?
Lower the voltage
Increase current
What does ∝ mean?
Directly proportional
What does AC stand for?
Alternating current
What particle carries the charge in an electric circuit?
The electron
How do you connect an ammeter to a circuit, in parallel or in series ?
In series
How do you connect a voltmeter to a circuit, in parallel or in series?
In parallel
What does a voltmeter measure?
A potential difference or voltage
Name the 2 non-ohmic components?
Filament bulb
Diode
What happens to the resistance of an LDR as the light intensity increases?
It decreases
What happens to the resistance of a thermistor as the temperature increases?
It decreases
What colour is the live wire on a 3-pin UK plug?
Brown
What colour is the neutral wire in 3-pin uk plug?
Blue
What colour is the earth wire in 3 pin uk plug?
Striped yellow ans green
What is the voltage in the neutral wire?
0V
Equation for current
I = Q/t
State 3 equations for power
P = V x I
P = I^2 x R
P = E/t
