Michelle has taught at the elementary level and has earned a master's degree.
One night a strong storm passed through Jacob's neighborhood. Suddenly, the entire house went dark. No lights, no sounds, nothing. Jacob had always been interested in electricity and this incident gave him a great idea for the upcoming science fair at his school.
He decided to show how electricity flowed through a circuit by using marbles and a clear plastic tube. Here, a circuit refers to the path between two points in which electricity flows.
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Jacob begins with voltage, the force that pushes electrons through a circuit to produce electricity. At the beginning of the circuit, electricity has a certain amount of force. It also has a certain amount of force at the end of the circuit.
The difference between these two amounts is the voltage, measured in volts. A small toy might take a 1.5-volt battery, but an excavator at a construction site requires a 24-volt battery.
To show this, Jacob uses one short and one long tube. He drops marbles down each one, with gravity representing the force or voltage. Which one do you think will have more volts at the end? The marbles going down the longer tube will have more because gravity had more time to act on it.
Next, Jacob demonstrates current, which is the act of the electrons flowing through the circuit. Each electron pushes the one in front of it, creating a continuous current. The higher the voltage, the faster the current.
This time the tubes are the same length. At the beginning of one tube, he uses a feather to push the marbles. For the other, he uses a pencil. In which tube will the marbles roll faster? The marbles that were pushed by the pencil will have a faster current because it had more force or voltage at the beginning.
Jacob's not done with current yet, because he wants to show two types of current, direct and alternating.
Direct current (DC) happens when electrons flow in only one direction. In Jacob's marble example, the marbles are put in on one end and exit on the other end. To keep the flow of electricity going, he would have to keep placing marbles down the tube. In reality, when the source runs out of electrons, there will no longer be an electrical current.
Electric cars use a direct current. Most things that use batteries, such as a toy, flashlight, cell phone, or any electronic uses direct current. Direct current flows at the same rate until a battery runs out.
Alternating current (AC) is different from direct current because electrons flow back and forth between two points. When the electrons change directions, the voltage drops. To show this, Jacob simply plugs the ends of the tube and tips it upside down when the marbles reach one end. This type of current reuses electrons.
Alternating currents are very useful in powering large things over long distances, like appliances, homes, hospitals, and office buildings. An alternator is a device that produces an alternating current, typically used in cars (except electric ones). It changes mechanical energy (from a battery) into electrical energy to power a car.
A circuit refers to the path between two points in which electricity flows. Voltage is the force that pushes electrons through a circuit to produce electricity. Current is the act of the electrons flowing through the circuit.
In a direct current, electrons only flow in one direction, while those in an alternating current change direction. An alternator is used in vehicles with gasoline engines to produce an alternating current.
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Voltage & Current Lesson for Kids
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