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Learn how voltage, current, and resistance are related in Ohm's Law. Explore circuit features like energy sources and conducting wires. Practice calculating voltage, current, and resistance in circuits.
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Bellringer • A standard household outlet has a voltage of what?
Electric Circuits • Part I
Ohm’s Law • Current, voltage, and resistance are related to one another. The relationship among resistance, voltage, and current is summed up in Ohm’s Law.
Ohm’s Law • Ohm’s Law states that the resistance of most conductors does not depend on the voltage across them. • Changing the voltage in a circuit changes the current but will not change the resistance. • Ohm concluded that conductors and most other devices have a constant resistance regardless of the applied voltage.
Ohm’s Law • The equation for Ohm’s Law is: • The units in the equation are: • Ohms (Ω) = Volts (V) ÷ Amps (A) Voltage or R=V/I Resistance = Current
Ohm’s Law • You can rearrange Ohm’s Law to find voltage with this equation: • Voltage = Current X Resistance • or • V=IR
Ohm’s Law • If a circuit has a resistance of 30.5 ohms and a current of .05 amps, what is it’s voltage? 1.525 volts
Ohm’s Law • The brake light on an automobile is connected to a 12-volt battery. If the resulting current is 0.40 amps, what is the resistance of the brake light? 30 Ω
Features of a Circuit • Circuits have devices that are run by electrical energy. • A circuit has a source of electrical energy. • Electric circuits are connected by conducting wires.
Features of a Circuit • Radios, appliances, and light bulbs are examples of electrical devices. All these devices resist the flow of electrical energy. As a result, electrical devices are known as resistors.
Features of a Circuit • Sources of electrical energy in a circuit include batteries, generators, and electric power plants. When you plug a radio into a wall socket, the source of electrical energy is your local electric plant.
Features of a Circuit • Conducting wires complete the path of an electric circuit. Wires allow charges to flow from the energy source to the electric device and back to the energy source.
Features of a Circuit • Often, a switch is placed in an electric circuit. With a switch, you can turn a device on or off by opening or closing the circuit.