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Fluorescent bulbs create a large potential difference between two electric plates.

# Electricity - Currents in Electrical Circuits

Electricity is a major topic in GCSE Physics. In this quiz we look specifically.at currents formed by the flow of electrons in electrical circuits.

From your studies of static electricity, you should by now be familiar with the idea that electricity is something to do with electrons. It seems that the ancient Greeks knew about static electricity - rubbing a substance called amber created a small force that could attract small objects. That was about the limit of knowledge until the scientific revolution in Europe during the Seventeenth Century. The physician to Elizabeth I, William Gilbert, experimented and described static electricity in many substances.

The origin of the word electricity is uncertain but it is thought to originate from the ancient Greek word for amber, elektron, in honour of the Greek discovery 2,000 years earlier. Amber is the fossilised resin of trees that is found in many places around the world. The largest source of amber is around the shores of the Baltic Sea and it is this amber that is used for jewellery. Occasionally amber contains beautifully preserved fossils of insects.

1.
What is the current through a circuit which contains three resistors of size 3 Ω, 5 Ω and 7 Ω respectively which are placed in series when a potential difference of 12 V is applied?
0.8 A
1 A
2 A
10 A
V = I multiplied by R so rearranging the equation gives I = V divided by R. The resistors are in series so the total resistance to use in the equation is the sum of the three individual resistors
2.
If the voltage in a circuit is increased whilst the resistance remains constant, what will happen to the current in the circuit?
Current decreases
Current increases
Current remains the same
Values for the voltage and resistance are required to answer this
Current and voltage are directly proportional
3.
Why does a 60 W equivalent fluorescent bulb use less energy than a 60 W filament bulb?
The electrons flow through the fluorescent bulb at a smaller voltage which reduces the energy used
The electrons flow through the fluorescent bulb with a smaller current, thus reducing the energy used
The fluorescent bulb has a smaller resistance than the filament bulb
They use the same amount of energy
Fluorescent bulbs create a large potential difference between two electric plates. The space between the plates is filled with an inert gas and when an electron gains enough energy to travel from one plate to the other, it can collide with the gas in the bulb. This creates an 'avalanche effect' where electrons are knocked out from the outer electron shells of the inert gas. The electrons are then absorbed by another atom and this process emits a photon of light. When the photons of light strike the coating on the inside of the bulb, the coating fluoresces, giving out light
4.
What is the definition of current?
Flow of atoms through a circuit
Flow of electrons through a circuit
The amount of resistance an electron experiences when travelling through a circuit
The energy which each electron has when flowing through a circuit
Metals are the best conductors of electricity because of metallic bonding
5.
What is the total resistance in a circuit if the potential difference is 12 V and the current flowing through the circuit is 3 A?
2 Ω
3 Ω
4 Ω
5 Ω
V = I multiplied by R so rearranging the equation gives R = V divided by I
6.
Two 2 Ω resistors are placed in parallel in a circuit. If the potential difference supplied to the circuit is 10 V, what size is the current which passes through each resistor?
5 A
10 A
20 A
40 A
Since the resistance is the same in the two parts of the parallel circuit, the current splits evenly. You can prove this to yourself by calculating from V = I R
7.
Calculate the current in a circuit when the voltage of the circuit is 5 V and the circuit has a total resistance of 5 Ω.
1 A
2 A
10 A
25 A
V = I multiplied by R so rearranging the equation gives I = V divided by R
8.
Two circuits are set up and both circuits contain two bulbs. One circuit is set up so that the bulbs are connected in series, whilst the other is set up so that the bulbs are connected in parallel. In which circuit will the bulbs be brightest if both circuits have the same resistance and the same voltage applied?
Circuit in parallel
Circuit in series
They will both have the same brightness
It is impossible to tell
Placing components in parallel reduces the resistance which each electron has to travel through to get to the positive anode of the cell, resulting in a larger current through each component
9.
If the voltage in a circuit remains constant but the resistance is increased, what will happen to the current?
Current decreases
Current increases
Current remains the same
Values for the voltage and resistance are required to answer this
The current and resistance are inversely proportional
10.
If two components are connected in series, how is the potential difference across each split?
It is dependent on which components are used.
It is dependent on the resistance of the components used.
One component gets twice as much voltage as the other.
They are the same.
Current, potential difference and resistance are closely linked. Each one depends on the value of the others
You can find more about this topic by visiting BBC Bitesize - Electric circuits

Author:  Martin Moore