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An LED emits light when the current flows through it in a forward direction.

# Electricity - Electrical Circuits 02

One of the main topics covered in GCSE Physics is electricity. In this quiz we look in particular at current, voltage and resistance in electrical circuits.

Circuits are electrical systems that provide a path for current to flow. If a circuit is broken, for example by using a switch, current is no longer able to move through it. If there is a short circuit, an electrical system will not work properly. A short circuit is a fault in a system that links two parts of a circuit that should not be linked together. In other words, it is a pathway that takes the electricity in the wrong direction.

Electrical circuits can have a wide range of applications; controlling your central heating; playing a door chime when the bell is pressed; inside computers and smartphones; controlling a car engine, and many, many more. They all follow the same straightforward laws, and it is how the components are arranged together that can make them do some pretty complicated things.

1.
An LED emits light when the current flows through it in which direction?
Forwards
Backwards
No current flow
Up and down
LED is the abbreviation for light emitting diode so from that, you should know that electrical charge can only flow through in the forwards direction through a diode
2.
How is the current of a resistor related to the potential difference across it?
Inversely proportional
Directly proportional
Equal
One-fifth of the potential difference
If the potential difference across a one ohm resistor is increased by one volt, the current will also increase by one amp
3.
The current through a component depends on which of the following?
The resistance of the component
The size of the component
The material of the component
The colour of the component
A bigger resistance means a smaller current. This is not the only factor affecting the current
4.
If two resistors are connected in parallel in a circuit, which has a total electrical potential difference of five volts, what is the value of the electrical potential difference across each resistor?
2.5 V
1.25 V
5 V
10 V
When two components are connected in parallel, they are connected to the same points of the circuit, so the electrical potential difference across each one is the same
5.
If two five ohm resistors are connected in series, what is the total resistance of the circuit?
5 ohms
10 ohms
2.5 ohms
7.5 ohms
Resistance of resistors in series are easy - just add up the individual values to get the total resistance
6.
If three 1.5V cells are connected in series, what is the total potential difference provided by the cells?
3 V
4.5 V
5.5 V
1.5 V
In series, just like with resistors, the voltages of the cells are added together
7.
Which equation correctly relates voltage, resistance and current?
R = IV
V= IR
I = RV
V = I R
This is how you write down Ohm's law mathematically
8.
What is the unit of resistance?
Ohm
Volt
Ampere
Coulomb
Ensure you always put units on the end of any question which asks for a numerical answer. The units of resistance are named after Ohm
9.
What can be found by measuring current and voltage?
Resistivity
Resistance
The direction of true north
Magnetic field strength
Measuring current and voltage lead German scientist Georg Simon Ohm to the conclusion that is now known as Ohm's law
10.
If a 100 ohm resistor is replaced with a 200 ohm resistor, whilst the potential difference is kept constant, what happens to the current?
Stays the same
Increases
Decreases
There is not enough information
Current is inversely proportional to resistance - as resistance is doubled the current is halved
You can find more about this topic by visiting BBC Bitesize - Electric circuits

Author:  Martin Moore

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