ELECTRICITY WITHIN A CIRCUIT Topic 2

Circuits Electric circuits provide a continuous pathway.

Circuit Elements and Diagrams Most complex circuits are made up of only four basic elements. Source: The source of electric energy. Conductor: The wire through which current flows. Load: Items along the circuit that convert electricity into other forms of energy. Control: A switch or device that can turn the circuit or devices along it on or off..

Circuit Elements and Diagrams A battery is a combination of cells. You can use a switch to “open” or “close” a circuit to control the flow of current through it. A resistor is used to represent one of many different loads.

Measuring Current Electric current is the amount of charge that passes a point in a conducting wire every second. The symbol for the current is I. Electric current is measured in amperes (A) or milliamperes (mA).

Measuring Current An instrument used to measure very weak electric current is called a galvanometer. Larger currents are measured with an ammeter of milliammeter. The symbols for these instruments are a circle with “G,” “A,” or “mA” in the center, respectively.

Measuring Voltage The energy for pushing electrons through comes from separated positive and negative charges. In a battery, energy from chemical reactions does the work of separating the charges. All forms of energy are measured in joules (J).

Measuring Voltage The energy of electrons in an electric circuit is described by a standard unit of charge instead of the total energy of all of the changes.

Measuring Voltage Potential difference means the difference in energy per unit of charge between one point in the circuit and another point in the circuit. Potential difference is commonly referred to as voltage. – The standard unit for potential difference is the volt (V), named after Alessandro Volta ( ), who built the first battery. Voltage is measured with a voltmeter; the symbol for a voltmeter is a circle with “V” at the centre.

Current and Voltage Electric current is equal throughout a circuit. For the electric current to flow in a circuit, the battery must be supplying energy & there must be a continuous pathway for the electric current to travel. Factors that affect the strength of an electric current in a circuit include the number of cells, voltage of the bulbs, type & length of the conductor, and the presence of loads.

Current and Voltage Batteries provide electrical energy. Loads use electrical energy. The energy provided to a circuit is very close to the energy used. The voltage across individual loads adds up to a voltage very similar to the voltage across the entire load. Voltage is higher when loads are removed because there is less resistance within the circuit.

Rivers of Electricity The load of an electrical circuit is comparable to a water wheel in a water system: – A switch is comparable to a valve – An electrical current is comparable to a flow rate – Voltage is comparable to pressure – A battery is comparable to a pump – A conductor (wire) is comparable to a pipe