Presentation on theme: "Chapter 7. Voltage Remember: Atoms are in EVERYTHING and they are made up of equal amounts of positive and negative charges. Battery: uses chemical energy."— Presentation transcript:
Voltage Remember: Atoms are in EVERYTHING and they are made up of equal amounts of positive and negative charges. Battery: uses chemical energy to move charges. If you connect a battery to an electrical device it will give up its stored energy to power that device (example a light bulb)
Voltage Voltage is a measure of electric potential energy, just like height is a measure of gravitational potential energy. Voltage is measured in volts (V). If a charge goes from 1 volt to 3 volts, it GAINS 2 joules of energy. If it drops from 3 volts to 1 volt it LOSES 2 joules of energy
Voltage A fully charged battery will add energy proportional to its voltage. (the positive end of the battery is 1.5 volts higher in energy than the negative end)
Voltage A battery uses stored chemical energy to create the voltage difference. Two 1.5-volt batteries can stack to make 3.0 volts. Three 1.5-volt batteries can be stacked to make a total voltage of 4.5 volts in a flashlight.
Voltage A pump is like a battery because it brings water from a position of low energy to high energy.
A useful meter is a multimeter, which can measure voltage or current, and sometimes resistance. To measure voltage, the meter’s probes are touched to two places in a circuit or across a battery.
Voltage Since voltage is measured, we usually assign the negative terminal of a battery to be 0 volts (0 V). This makes the voltage of every other place in the circuit relative to the negative end of the battery.
Voltage Voltage is reduced when energy is used. 0.75 Volts
Current Electric current is caused by moving electric charge. Electric current comes from the motion of electrons.
Current Electric current is similar in some ways to a current of water. Like electric current, water current can carry energy and do work. A waterwheel turns when a current of water exerts a force on it.
Current Current only flows when there is a complete and unbroken path, or a closed circuit. Flipping a switch to the “off” position creates an open circuit by making a break in the wire.
Current Electric current is measured in units called amperes, or amps (A) for short. One amp is a flow of a certain quantity of electricity in one second. The amount of electric current entering a circuit always equals the amount exiting the circuit.
Current If you want to measure current you must force the current to pass through the meter. Multimeters can measure two types of current: alternating current (AC) and direct current (DC).
Resistance Resistance is the measure of how strongly an object resists current flowing through it. The relationship between electric current and resistance can be compared with water flowing from the open end of a bottle.
Resistance The total amount of resistance in a circuit determines the amount of current in the circuit for a given voltage.
Electrical resistance is measured in units called ohms. This unit is abbreviated with the Greek letter omega (Ω). Resistance