Electrical current
There are two types of Moving electric charges, eg electrons moving through a metal wire.: direct and alternating. In a Direct current is the movement of charge through a conductor in one direction only. (dc), the flow of Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. is consistently in one direction around the circuit. In an Also called ac. An electric current that regularly changes its direction and size. (ac), the direction of electron flow continually reverses.
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Charge
Electrons are negatively charged particles and they transfer energy through wires as electricity.
Property of matter that causes a force when near another charge. Charge comes in two forms, positive and negative. For example, a negative charge causes a repulsive force on a neighbouring negative charge. is a property of a body which experiences a force in an electric field. The flow of charge is measured in Unit of charge. Eg the charge on an electron is 1.6 × 10-19 coulombs. (C).
Since electrons are so small and one electron will not have much of an effect anywhere, it is more useful to refer to packages of electrons. One coulomb of charge is a package equivalent to 6,250,000,000,000,000,000 electrons.
Current
When current flows, electrical Energy transferred by a force. Work done = force × distance moved in the direction of the force. is done and energy transferred. The amount of charge flowing past a point in the circuit can be calculated using the equation:
charge flow = current × time
\(\text Q = \text I \times \text t\)
This is when:
- charge flow (\(\text{Q}\)) is measured in coulombs (C)
- current (\(\text{I}\)) is measured in amperes or amps for short (A)
- time (\(\text{t}\)) is measured in seconds (s)
One amp is the current that flows when one coulomb of charge passes a point in a circuit in one second.
Example
A current of 1.5 amps (A) flows through a simple electrical circuit.
How many coulombs of charge flow past a point in 60 seconds?
\(\text Q = \text I \times \text t\)
\(\text{Q}\) = 1.5 × 60
\(\text{Q}\) = 90 C
Question
How much charge has moved if a current of 13 A flows for 10 s?
\(\text Q = \text I \times \text t\)
\(\text{Q}\) = 13 × 10
\(\text{Q}\) = 130 C
Question
How much current flows when 10 C passes down a wire in 2 s?
\(\text Q = \text I \times \text t\)
\(\text{I} = \frac{\text{Q}}{\text{t}}\)
\(\text{I} = \frac{10}{2}\)
\(\text{I}\) = 5 A
Measuring current
Current is measured using an A device used to measure electric current.. To measure the current through a component, the ammeter must be placed in A circuit where one component follows directly from another, eg three bulbs in a row with no junctions are said to be connected in series. with that component.
Charge will only flow in a circuit if the circuit is closed, or complete, and if there is a potential difference applied to the circuit either by using a power supply or a battery.
More guides on this topic
- Motion - AQA Synergy
- Newton's laws - AQA Synergy
- Mains electricity - AQA Synergy
- Acids and alkalis - AQA Synergy
- Rates of reaction - AQA Synergy
- Energy, rates and reactions - AQA Synergy
- Equilibria - AQA Synergy
- Electrons and chemical reactions - AQA Synergy
- Sample exam questions - movement and interactions - AQA Synergy
