Simple Circuits. Series and Parallel Circuits. Learning Intentions. Understand the role of the energy source in a circuit. Understand how electricity flows through a circuit Be able to construct series and parallel circuits Understand what current and voltage is.
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Series and Parallel Circuits
Galvani was preparing frog legs for his wife who was ill. He hung them from an iron rail at the edge of a balustrade by a copper wire.
Each time the wind blew or some other force would cause the prepared legs to swing and touch the iron they would suddenly contract as if alive.
Galvani knew that electric shocks caused the convulsive movement but he did not know what caused the electricity to flow.
He developed a theory of animal electricity i.e. a life force within the muscles of the animal itself.
At the University of Pavia, Galvani's colleague Alessandro Volta was able to reproduce the results, but was skeptical of Galvani’s explanation. By experiment Volta found that it was two dissimilar metals, not the frog’s leg that produced the electricity. The frog’s leg was just an indicator of the presence of electricity. i.e. current flowed through the frog’s legs.
Source of electrical energy e.g. battery
User of electrical energy e.g. light globe
= Charged particle/electron
Current in a Simple Circuits
For an electric current to flow there needs to be a path from the positive terminal of the battery into and out of the circuit components (e.g. light globe) and back to the negative terminal of the battery
“What's Happening?” Sheet
Simple Circuits summary
Fig 1: Series Circuit
Fig 2: Parallel Circuit
Example - If a current of 5 A flows through a globe, this means 5 coulombs of electrons pass through one globe each second.
What do you notice in each case
Measures the voltage or potential drop between two points in a system
Which horse has the greater potential energy?
Which horse has the lower potential energy?
Is there a difference in potential gravitational energy between horses A and B?
The horse at the top of the side has the potential to slide down to the bottom. In the process, the horse’s potential gravitational energy can be changed to kinetic, heat and sound energy.
The electron has the potential to move around the circuit. As it does so, its electrical potential energy will be changed to kinetic, light and heat energy.
Which horse on the slide has the greatest potential gravitational energy? Is their a potential difference between the two horses?
Which electron A or B , has the greatest electrical potential energy?
Is there a potential difference between the electrons?
The two slides are the same length. Which horse would move fastest?
Which electron would move fastest around the circuit?
On slide B thoughtless people have left their rubber mats. Which horse, A or B, will move fastest down the slide?
Which electron would meet the greatest resistance to go around the circuit?
In order to go around the circuit again, the electron must pass through the battery. In the battery chemical energy is changed into potential electric energy which can be used by the electron as it goes through the circuit.
In order to go down the slide again, a horse must climb up the steps. In the process, kinetic energy is changed into potential gravitational energy.
The difference in electrical potential of a unit of charge at one point in a circuit, compared with a unit of charge at another point is called the potential difference (p.d.) or voltage drop, or more usually just voltage (V). It is measured in volts using a voltmeter. The largest potential difference in a circuit is between the terminals of the battery or power supply.
Role play demonstrating energy used in a series and parallel circuit when components use same amount of energy different amounts of energy