13.5: Potential Difference
pg. 560
Key Concepts:
3. Potential difference is a measure of the difference in electric potential
energy per unit of charge between two points.
- During trouble shoot circuits, the first thing Electricians will check is
current; the next thing is to determine the potential difference (voltage)
within the circuit.
- The unit of measure for potential difference is volt (V).
Potential Difference (voltage) (V): is the difference in electric potential
energy per unit charge measured at two different points; measured in volts
(V).
A Model for Electric Potential Energy
- Potential difference is the difference between two points within a circuit or
the difference between the two electrodes of an electric cell.
- Electrons within a circuit leave the negative electrode with more energy
then when they return to the positive electrode.
- The difference is the energy lost as a transformation to do work by a load.
- The water wheel uses gravitation pull. As the water falls from a higher
point to a lower point it is able to turn the wheel. The greater the difference
between the two points, the greater the speed of the wheel turning.
Figure 2: a) A pump provides potential energy to the water, which can then
turn a waterwheel, b) A potential difference is necessary for current to flow
in a circuit. Within the battery, the electrons flow from the negative
electrode (higher electric potential energy) to the positive electrode (lower
electric potential energy)
Measuring Potential Difference
Voltmeter: a device used to measure potential difference (voltage).
- A voltmeter is a device used to measure potential difference.
- When a voltmeter is connected to measure the voltage in a circuit, it must
be connect in parallel, around the load or energy source.
- The voltmeter measures the difference between points in the circuit.
Figure 4: A voltmeter measures the potential difference across the lamp.
Evidence of Learning …. Students can
- explain how to connect a voltmeter to a circuit.
- identify a battery, voltmeter, and lamp in a circuit diagram.
- explain the similarity between potential difference in an electrical circuit
and a waterwheel being powered by falling water.
Check Your Learning
Questions 1 – 4, page 561
Summary:
- Potential difference, or voltage, is the difference in electric potential energy
per unit charge measured at two points.
-Electrons flow from a point of higher electric potential energy to a point of
lower electric potential energy.
- Potential difference is measured in volts (V) using a device called a
voltmeter.
-Voltmeters must be connected in parallel with either a load or an energy
source when measuring potential difference.