BBC Bitesize - KS3 Physics - Electric current and potential difference - Revision 1
a) Show that the current I is 25 mA. (2 Marks). b) Calculate the potential difference (p.d.) across the resistor of resistance Ω. p.d. = . V. (1 Mark). Learn how electric circuits and how to measure current and potential difference with BBC Bitesize KS3 Science. Ohm's Law is a statement of A. the relationship between current, resistance, and potential difference. B. the relationship between current, resistance, and area .
The current is worked out from the quantity of charge flowing divided by the number of seconds it takes it to pass a defined point in a circuit. Moving electrical charge through a circuit needs work to be done - the greater the resistance, the greater the energy required. The energy is supplied by the power source for the electrical circuit.
As the charge moves through the circuit, some of the energy it carries is transferred. In the wires, it is transferred to heat and wasted. In a component such as an LED, it is transferred into heat and also directly into light, which is the useful energy. Electrical potential difference is a measure of the energy transferred as the charge passes through a component and has the units of volts V.
One volt of electrical potential difference represents one coulomb of charge gaining or losing one joule of energy.
When you plot a graph of the current flowing through a component against the electrical potential difference, you end up with a current-potential difference graph. When asked about electricity in the GCSE, you should be able to recognise the shapes of graphs for a resistor at constant temperature, a diode and a filament lamp.
EMF, Potential Difference And Current
The examiners may put one in for a component for which you have never seen the graph, but you will be told what it is and be asked some simple questions about the information you can get from it. What is the formula for potential difference? Eventually, scientists became aware that there was another form of electricity - current electricity.
We now understand electricity much batter and know that electrical currents are formed by the flow of electrons through electrical circuits.
An electrical circuit consists of a closed loop of conductors connected to a source of a potential difference such as a battery or generator. A potential difference has two aspects, positive and negative; it can sometimes help to think about it as being an electron pump.
Additional Electric Current And Resistance - ProProfs Quiz
Electrons have negative charge and so will flow away from the negative pole and be attracted to the positive pole. Just to confuse things, when current electricity was first discovered, scientists had no idea bout what it was. They realised it was a flow of something and decided that it went from positive to negative - we call this conventional current and this idea is still used when designing and talking about electrical circuits.
The ability to control the currents in electrical circuits has allowed us to create an astonishing variety of electronic products. The current flowing in a circuit depends on two variables, the potential difference voltage and the resistance. In a circuit, where it reaches a junction, the current will divide and flow down each of the parts of the circuit linked to the junction.
The amount of current flowing through each part can be calculated using Ohm's law.
Electricity - Electrical Circuits 01
For your GCSE, you are expected to be able to use this to calculate current, potential difference and resistance in all or part of a circuit. To do this, you need to be able to rearrange the terms of the equation. If the potential difference supplied to the circuit is 10 V, what size is the current which passes through each resistor?
Why does a 60 W equivalent fluorescent bulb use less energy than a 60 W filament bulb?