Electricity and circuits T5 Flashcards
What is current?
The flow of electric charge around a circuit. Unit : ampere
What is the potential difference?
The potential difference (or voltage) is the driving force that pushes the charge around. Unit : volt. The potential difference is the energy transferred per coulomb of charge
What is resistance?
Resistance is anything that slows the flow down. Unit : ohm
What happens when there is a high potential difference?
There is a high current
What will happen if there is a high resistance?
There will be a low current
How do you work out charge?
Charge = current x time
What unit is charge in?
Coulombs
How do you work out energy transferred?
Energy transferred = charge moved x potential difference
How to work out resistance?
Resistance = potential difference / current
What does an ammeter do?
This measures the current (in amps) flowing through the component. It can be put anywhere in the main circuit
What does a volt meter do?
This measures the potential difference across the component. It must be placed under parallel with the component under test
What do linear components have on an iv graph?
A straight line
What do non - linear components have on an iv graph?
A curved line
How to work out the resistance on an iv graph?
The resistance will be the inverse of the gradient or 1/gradient. The steeper the graph the lower the resistance
What is an ldr?
An ldr ( light dependent resistor) is a resistor that is dependent on the intensity of light. In bright light, resistance falls. In darkness, the resistance is highest
What is a thermistor?
A thermistor is a temperature dependent resistor. In hot conditions, the resistance drops. In cool conditions, the resistance goes up
Which way do electric field lines travel?
Positive to negative
Which way do electric filed lines face?
At a right angle to the surface
What do close filed lines represent?
A stronger electric field
How do photocopiers work?
They use static electricity the copy images onto a charged plate before printing them
How do electrostatic sprayers work?
Bikes and cars are painted using electrostatic paint sprayers. The spray gun is charged, which charges up small drops of paint, each drop repels all others, so you get a very fine, even layer of paint over the the bike or car
How can static electricity be dangerous when refuelling a car?
A fuel flows out of a fuelling pipe, eg a aircraft or tanker, then static electricity can build up, this can easily cause a spark which can lead to an explosion
What happens when electric charge builds up on an object?
The potential difference between the object and the earth increases, if the potential difference gets large enough, electrons can jump across the gap between the charged object and the earth
What happens with 2 things with opposite electric charges?
They are attracted to each other
What happens to 2 electric things with the same charge?
The repel each other
What happens with insulating materials are rubbed toegther?
Negatively charged electrons will be scraped off one and dumped on the other, as the materials are insulators, these electrons are not free to move, this build up of charge is static electricity
What is a series circuit?
In a series circuit, the different components are connected in a line, end to end. If you disconnect 1 component, the circuit is broken
What is a parallel circuit?
In parallel circuits, each component is separately connected to the power, if you move or disconnect one of them it will hardly change the others at all
What happens to the p.d. And the current in a series circuit?
Theres a bigger p.d when there are more cells in a series, e.g 2 batteries with 1.5 v supply 3 v. The current is equal everywhere I1 = I2 = I3
What happens to the p.d and the current in a parallel circuit?
In a parallel circuit, the potential difference is the same across all components v1 = v2 = v3. Current is shared between branches. The total current flowing around the circuit is equal to the total of all the currents through the separate components. Itotal = i1 + i2
What happens when you add a resistor in a series circuit?
The total resistance increases because by adding a resistor, the two resistors share the total p.d
What happens when you add a resistor to a parallel circuit?
The total resistance decreases because, if you have 2 resistors in parallel, their total resistance is less than the resistance of the smallest of the 2 resistors
How do you work out energy transferred?
Energy transferred = current x p.d x time
How is energy transferred in a kettle?
The energy is electric which then transfers to the thermal energy of the kettle
How do you work out power?
Power (w) = energy transferred / time
How do you work out electrical power?
Electrical power = current x p.d
What is an a.c?
In a.c supplies the movement of the charges is constantly changing direction. Alternating currents are produced by alternating voltages
What is a d.c?
In direct current the movement of the charges is only in 1 direction. Its created by a direct voltage
What is the live wire?
Brown, the live wire carries the voltage. Goes up to 230 v
What is the neutral wire?
Blue the neutral wire completes the circuit, electricity normally flows in through the live and out through the neutral wire. The neutral wire is always at 0v
What is the earth wire?
Green and yellow, the earth wire is for safety and protecting the wiring. It carries the current away if something goes wrong and stops the appliance casing going live. Its also at 0v
What is an electric shock?
Your body is at 0v, this means that if you touch the live wire, a potential difference is produced across your body and a current flows through you. This causes a large electric shock which could kill you
How does a fuse work?
When a voltage gets too high, the fuse wire melts so that no more electricity can come through
What is a circuit breaker?
Instead of a fuse wire, the circuit breaker may just trip something to the power of. Circuit breakers turn off quicker than fuses do and can be reset, but are more expensive
