Section 4 Ohm’s law: The resistance is equal to the voltage divided by the current. Resistance= Voltage Current You can use this formula to see how changes in resistance, voltage, and current are related. Circuits have devices that are run by electrical energy. These devices transform electrical energy into another form of energy. Example: Light bulb transforms electrical energy into electromagnetic and gives off light. Light bulbs and fans are resistors because they resist the flow of electric current. A circuit has a source of electrical energy. Batteries, generators, and electric plants are sources of electricity. Electric Circuits are connected by conducting wires. The conducting wires complete the path of the current and allow charges to flow from the energy source to the device. In a series circuit, there is one path of energy for the current to take. The part are connected one after another. Very simple to design and build What happens if one bulb in series burns out? Why? Resistor: the more light bulbs you add to a series circuit, the dimmer the light bulbs will be. Ammeter: Device used to measure current. Parallel Circuits provide several paths for the flow of electrons. Each bulb is connected by a separate path from the battery. If one bulb burns out, the others will be able to stay lit. Resistance decreases in a parallel circuit. A voltmeter is a device used to measure voltage or electrical potential energy difference.