Activity #2: Series and Parallel Circuits
What are Series and Parallel Circuits??
Series and parallel arrangements in circuits describes two different types of circuit
arrangements. Each arrangement provides a different way for electricity to flow through a
circuit.
Series Circuit The circuit illustration shown below is a simple series circuit containing a battery, few wires and
two light bulbs. The flow of electricity is caused by excess electrons on the negative end of the
battery flowing towards the positive end, or terminal, of the battery. When the circuit is complete
electrons, flow from the negative terminal through the conducting wires to the bulbs (lighting it
up) and finally back to the positive terminal – in a continual flow.
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Definition of a series circuit:
A circuit that contains only one possible path for electron flow supplied by a common
voltage source.
A series circuit is wired with only one path for the current to flow through all the devices in a
row and back to the starting point. The same current flows through each part of a series circuit. If
the circuit is broken at any point there won’t be any current that will flow. In the above circuit,
electricity flows from the battery to each bulb, one at a time, in the order they are wired to the
circuit. In this case, if one of the bulbs blew out, the other bulb would not be able to light up
because the flow of electric current would have been interrupted. In the same way, if one of the
bulb was unscrewed, the current flow to both the bulbs would be interrupted. If the circuit were a
string of light bulbs, and one burned out, the remaining bulbs would also turn off.
The schematic diagram of the above circuit showing the electronic symbols for the battery, and
bulbs is shown below.
Parallel Circuit The circuit illustration shown below is a simple Parallel circuit containing a battery, few wires
and two light bulbs. The flow of electricity is caused by excess electrons on the negative end of
the battery flowing towards the positive end, or terminal, of the battery. When the circuit is
complete electrons, flow from the negative terminal through the conducting wires to the bulbs
(lighting it up) and finally back to the positive terminal – in a continual flow.
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Definition of a Parallel circuit:
A circuit that contains two or more paths possible paths for electron flow supplied by a
common voltage source.
A parallel circuit is wired with two or more paths for the current to flow through all the devices
and back to the starting point. In the above example, two bulbs are powered by a battery in a
parallel circuit design. In this case, because electricity can flow in more than one path, even if
one of the bulb blows out, the other bulb will still have electrons flowing through it and it will
continue to glow. In the same way, if one of the bulb is unscrewed, it would not prevent the other
bulb from lighting up. If the circuit were a string of light bulbs, and one burned out, the
remaining bulbs would continue to be lit. Parallel circuits are the types of circuits, that are found
in a house. Obviously, when you turn off your lamp, it doesn't turn off your TV. Connecting
bulbs in parallel allows each to shine equally brightly.
The schematic diagram of the above circuit showing the electronic symbols for the battery, and
bulbs is shown below.
What is Resistance???
The flow of electrons or electricity depends on how much resistance is in the circuit. In the above
cases the bulbs provided the resistance. In a series circuit, the resistance in the circuit equals the
total resistance of all the bulbs. The more bulbs in the circuit, the dimmer they will be lit. In a
parallel circuit, there are multiple paths through which the current can flow, so the resistance of
the overall circuit is lower than it would be if only one path was available. The lower the
resistance means that the current will be higher and the bulbs will be more brighter compared to
the same number of bulbs arranged in a series circuit.
What are bulbs??
Light bulbs have a very simple structure. At the base, they have two metal contacts, which
connect to the ends of an electrical circuit. The metal contacts are attached to two stiff wires,
which are attached to a thin metal filament. The filament sits in the middle of the bulb, held up
by a glass mount. The wires and the filament are housed in a glass bulb, which is filled with an
inert gas, such as argon.
When the bulb is hooked up to a power supply, an electric current flows from one contact to the
other, through the wires and the filament. Electric current in a solid conductor is the mass
movement of free electrons (electrons that are not tightly bound to an atom) from a negatively
charged area to a positively charged area.
As the electrons zip along through the filament, they are constantly bumping into the atoms that
make up the filament. The energy of each impact vibrates an atom -- in other words, the current
heats the atoms up. A thinner conductor heats up more easily than a thicker conductor because it
is more resistant to the movement of electrons.
Bound electrons in the vibrating atoms may be boosted temporarily to a higher energy level.
When they fall back to their normal levels, the electrons release the extra energy in the form of
photons. Metal atoms release mostly infrared light photons, which are invisible to the human
eye. But if they are heated to a high enough level -- around 4,000 degrees Fahrenheit (2,200
degrees C) in the case of a light bulb -- they will emit a good deal of visible light.
The filament in a light bulb is made of a long, incredibly thin length of tungsten metal. In a
typical 60-watt bulb, the tungsten filament is about 6.5 feet (2 meters) long but only onehundredth of an inch thick. The tungsten is arranged in a double coil in order to fit it all in a
small space. That is, the filament is wound up to make one coil, and then this coil is wound to
make a larger coil. In a 60-watt bulb, the coil is less than an inch long.
Tungsten is used in nearly all incandescent light bulbs because it is an ideal filament material
Materials:
3 AA batteries
Battery holder
3 bulbs (6.3V) and 3 bulb holders
Connecting wires with alligator clips
Switches like paper clips
Procedure:
1. First draw the simple circuit with one bulb, then make predictions on how it would work,
then build your circuit, make observations and then explain.
2. Carry out the same procedure with two bulbs and three bulbs in series.
3. Carry out the same procedure with three bulbs in series.
4. Brainstorm different ideas to build combination circuits.