Current electricity Ch. 34 Coulomb is the unit of charge abbreviated, C. 1 Coulomb is the charge on 6.25 billion electrons.

Electrical Current Electrical current is the flow of electrons. The rate of electrical flow is measured in Amperes ( A ). An ampere is the rate of flow of 1 coulomb of charge per second.

Electric Current Electrons flow in a wire only when a difference in electrical pressure exists. The name for electrical pressure is volt. Voltage is the name for electrical pressure. Current flows in a wire when there is a difference in voltage across the ends of the wire.

Electrical Current How much current also depends on electrical resistance. A narrow wire resists electrical current more than wider wire. Electrical resistance is measured in Ohms. Superconductors are materials that have zero resistance at low temperatures

Electrical Current Electrical current may be direct or alternating. DC means direct current. This is the current made up of electrons moving in one direction.

Electrical Current A battery produces direct current in a circuit because the terminals of the battery always have opposite charges. Electrons move form the negative terminal in which the electrons repel toward the positive terminal which they are attracted to.

Electrical Current AC means alternating current. Electrons in the circuit flow initially in one direction and then in the opposite direction. This is done by switching the sign at the terminals of the power station generator. AC is responsible for most commercial electricity.

Watt’s Happening? Power is the energy being transformed. Electrical energy can be transformed into mechanical energy (motor), light energy (lamp), or thermal energy (heat). Power = current x voltage When current is in amperes and voltage is in volts, then power is in watts.

Electric current

Electrical Circuits Any path along which electrons can flow is a circuit. Circuits can be wired in series or parallel.

Electric circuits

Series circuits Req = R1 + R2 + R3 + ...

Parallel circuits

Series/parallel connections

equivalent resistance of resistors in series : Re = R1 + R2 + R3 + ...

equivalent resistance of resistors in parallel: 1 / Re = 1 / R1 + 1 / R2 + 1 / R3 +...

1. Observe the electrical wiring below 1. Observe the electrical wiring below. Indicate whether the connections are series or parallel connections. Explain each choice. Diagram A: Parallel There is a branching location in the circuit that allows for more than one pathway by which charge can flow through the external circuit. Diagram B: Series There is no branching in the circuit - that is, no location where one wire leads into a point and branches off into two or more wires at that particular point.

Power

Here is a simple electric circuit. It has a cell, a lamp and a switch Here is a simple electric circuit. It has a cell, a lamp and a switch. To make a circuit, these components are connected together with metal connecting wires. When the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.