Lesson 2 Summary: Electric Current and Simple Circuits

The movement of electrically charged particles (electrons) is an electric current.

A closed, or complete path in which an electric current can travel is called an electric circuit.  

• If the circuit is closed, then there is a complete path and the electricity will flow.

• If the circuit is open, then there is some break or gap in the circuit, and the electricity will NOT flow.

The battery serves as a storehouse of electrical energy.  Chemical potential energy is stored here and turned into electrical energy as electrons flow through the complete circuit.

In a simple, closed circuit, electrons flow from the negative end of the battery, through the wires, through any electrical devices that the circuit powers, and back through more wires to the positive end of the battery.

A couloumb is how scientists count the number of electrons in a circuit.  Since electrons are so small, we use Coulombs of charge to describe them.  One Coulomb of electrons is about 6 x 10¹⁸, or 6 quintillion.

Current is the measure of how much charge is flowing through a circuit at any given moment.  

• We can think of current as being similar to water flowing out of a faucet.

• In the metric system, current is measured in Amperes.

• 1 A of current means that 1 coulomb of charge flows through a wire every second.

Resistance is a measure of how difficult it is for electrons to flow through a material.

• ALL electrical devices operate on the idea of resistance.  It’s how we get useful work from electricity.

• The more resistance in an electrical circuit, the greater the workload on the electrons.

• In the metric system, resistance is measured in Ohms.

A good conductor of electricity has low resistance.  A poor conductor of electricity has high resistance.

Thicker wires have lower resistance than do thinner wires.  Longer wires have higher resistance than shorter wires.

Voltage is the amount of energy the source uses to move electrons through an electric circuit.  Voltage is the “push” on the electrons, forcing them through the circuit.

• In the metric system, voltage is measured in Volts.

• The more voltage, the stronger the forward push on the electrons.

Batteries offer voltage of between 1.5-9 V.  Wall outlets offer voltage of about 120 V.

Ohm’s Law tells us the relationship among current, voltage and resistance in a circuit.

• The greater the voltage in the circuit, the greater the current will be.  Voltage and Current are directly proportional.  

  • This makes sense because if you push the electrons harder, they’ll go faster.

• The greater the resistance in the circuit, the less the current will be.  Resistance and Current are inversely proportional.  

  • This also makes sense because if you make the electrons work harder, they won’t want to move as fast.