Download here: Ontario Curriculum Expectations
The most beautiful thing we can experience is the mysterious.
Albert Einstein
Review your electric vocabulary (and learn something new!) by watching the video below:
An electric circuit is made up of four basic parts: a power source, a load, a wire, and a switch.
The power source pushes the electricity through the wire which carries it to the load. The load converts the electrical energy into light, or heat, or sound, or motion, or whatever it is designed to do, and finally, the switch regulates the flow of the electricity.
The short line on the power source symbolizes the negative terminal and the long line symbolizes the positive terminal.
How Electricity Moves Around a Circuit:
Potential Difference (or Voltage): is the amount of energy carried through the circuit per unit of charge. Potential difference and voltage are two words for the same thing. The greater the potential difference, the more energy will be provided to the circuit. It is the potential difference that drives the current around the circuit. We use the symbol “V” to represent potential difference and it is measured in Volts (V).
Current: is the rate at which charge is carried around the circuit. It gives us a measure of how fast the electrons are flowing around the circuit. We use the symbol “I” for current and it is measured in Amperes, or Amps (A) for short.
Resistance: slows down the flow of electricity. In most electrical circuits, the load provides the resistance. The larger the load, the more the electricity is slowed down. We use the symbol “R” for resistance and it is measured in Ohms (?).
There are two different ways of looking at how electricity flows around a circuit. The first way is the electron flow model. According to this model, the electricity flows from the negative terminal, around the circuit and back to the positive terminal. This is how the electrons flow around the circuit.
The electron flow model is illustrated by the red arrow. It shows the direction that electrons flow around the circuit.
The conventional flow model is illustrated by the green arrow.
The second way is called the conventional flow model. According to this model, the electrical current flows from the positive terminal, around the circuit and back to the negative terminal. In this course we will be using the conventional flow model.
Voltage, current, and resistance are related through Ohm’s Law. Complete the Ohm’s Law multimedia element before returning to this content page.
Ohm’s Law:
Ohm’s Law states that:
In an ideal conductor, the potential difference between any two points is proportional to the current between the two points if the temperature stays the same. The proportionality constant is equal to the resistance.
This can be written much more concisely as:
or V = IR
Where,
V = potential difference measured in volts (V)
I = current measured in Amps (A)
R = resistance measured in Ohms (?)
Example 1:
A circuit is set up with a 6.0 V power supply. If the resistance of the load connected to the circuit is known to be 48.0 ?, what is the current flowing through the circuit?
Given:
V = 6.0 V
R = 48.0 ?
Required:
I = ?
Solution:
I = 0.125 A
The current through the circuit is 0.125 A.
Practice Questions
- When a toaster is connected to a 120 V power supply, there is 8.3 A of current running through it. Calculate the resistance of the heating coil in the toaster.
Answer
Given:
V = 120 V
I = 8.3 A
Required:
R = ?
Solution:
The resistance of the heating coil in the toaster is 14.5 ?.
Learn more about Ohm’s Law.