Circuits Flashcards
In a circuit how do you measure potential difference or current?
You measure potential difference (voltage) by connecting a voltmeter in parallel. You measure current by connecting an ammeter to the circuit.
Difference between circuits:
Series vs parallel
In a parallel circuit they are separately cone cited to the positive and negative supply whereas in a series circuit they are connected together. This means that if a wire is unplugged in a series it will disrupt the whole circuit however in parallel they remain unchanged.
In a parallel, they have a equal voltage across each component but current is shared.
In a series, they have a equal current in the circuit but voltage increases when more cells are added into the circuit.
What happens to a circuit when you add a resistor?
In a series circuit, the total resistance increases as the two resistors have to share the total potential difference.
In a parallel circuit, the total resistance decreases as the current has two different directions to travel in increasing the current.
What happens when an electrical charge goes through a change in potential difference?
Energy is transferred, the larger the current through or potential difference across a component means that more energy is transferred.
How is energy transferred from cells?
They are designed to transfer energy to components in the circuit when a current flows.
What does heating do to a circuit?
In general, heating generally reduces its efficiency-less energy is transferred to useful energy stores because more of it is being transferred to the thermal energy store, if it gets too hot the circuit components will melt.
Although, if you want to heat something, e.g. Bread, if it has a high resistance the current passes through the coil and it gives our infrared radiation. This transfers energy to the bread and cooks it.
What does energy transferred rely on?
Power. The total energy transferred by an appliance depends on how long the appliance is on for and the power.
What is a power rating? What does it help us do?
This is the maximum safe power that they can operate at. It tells you the maximum energy transferred per second. It helps customers choose between models but it doesn’t necessarily mean that it transfers energy usefully.
What does power depend on?
Current and potential difference. Both of these will affect the rate that energy is transferred to an appliance, and the rate it transfers energy to other sources.
What are the two different energy supplies?
Alternating current and direct current.
A.c supplies is constantly changing direction, this is how the mains supply, of 230v, supply our homes
D.c supplies is always flowing in the same direction.
What are the three core cables in a plug?
Brown: The live wire > carries electricity from the mains of 230v
Blue: The neutral wire > carries electricity back to the mains 0v
Green and yellow: The earth wire > it is for safety, if anything happens it carries the current away and stops the appliance casing becoming live 0v.
How does earthing and fuses prevent electrical overloads?
Surges in current occurs because of changes in the circuit or because of a fault. If this happens the fuses either melts absorbing the overload of current or the earth wire redirects the current down the cable. When a fuse melts it cuts off the circuit as it is direct to the live wire.
How are circuit breakers better than fuses?
- instead of melting they turn off creating a quicker and renewable source of safety
- although it is more expensive
Circuit symbols:
Look at book
