1. What is a circuit made up of?
2. List the importance of circuits.
3. What do you understand by lighting effect and heating effect of
electric current?
4. Describe the different types of electric bulbs? Which one is the
most energy efficient?
5. How are circuit breakers similar to fuses? How are they not
similar? Which one is more convenient to use?
6. List the various uses of an electromagnet
Answers
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1. A circuit typically contains the following parts:
• A voltage source: A cell or a battery provides the electric potential
for the electric charge to flow through the circuit.
A power plant may also be a source of voltage for a household.
• A conductor: A conductor is a wire that connects the voltage source
to the appliance and back. We use good conductors as conducting
wires as we do not want to lose electrical energy as heat.
• A switch: This is a device that can complete or break the circuit. It
creates a gap so the charge cannot flow and then the circuit is said to
be open. If the charge flows, then the circuit is said to be closed.
• Electrical device: This is any appliance that changes electrical energy
into any other form of energy (bulb, fan, fridge and light) for a useful
purpose.
2. Circuits are important:
a. Circuits connect a power source to an electrical device to allow the device
to work and allow us to use electric current.
b. Electrical devices, connected in a circuit, convert electrical energy into
other forms of energy and can be used in many ways.
➢ Electric current converted to heat energy - radiant heater
➢ To mechanical energy - fan
➢ To sound energy - music system
➢ To electromagnetic energy - doorbell
➢ To light energy- bulb
c. Circuits are constructed for specific purposes in different devices. The
circuit in an electric iron is different from that in a cell phone.
d. Circuits can have multiple paths. For example, in a CD player, the electric
circuit supplies current to a circuit that changes electricity to sound, to light
up the LED screen and opens the CD lid.
3. ➢ Lighting effect of electric current:
• Conversion of electrical energy to light energy is called lighting effect of electric current.
• Some electrical energy also gets converted to heat energy; this is wasted energy as it cannot be used.
• A bulb converts electrical energy to light energy. During this conversion, some electricity also gets converted into heat energy.
• Electrical energy passes through a wire filament, usually made of
tungsten. The filament becomes hot and begins to glow.
➢ Heating effect of electric current:
• Conversion of electrical energy to heat energy is called heating effect of electric current.
• The heating effect of an electric current depends on the type of wire of the conductor the thickness of the wire, the length of wire, the amount of current being used and the duration it is used for.
• The heating element is made of Nichrome wire-alloy of Nickel 80% and Chromium 20%, has high resistance and heats up.
• We use this property of converting electrical energy to heat energy in many of our appliances at home like room heater and bread toaster etc.
4. Generally there are three types of electric bulbs:
➢ Filament bulbs (incandescent bulbs):
• Are usually powered through a wire filament made of tungsten.
• The filament becomes hot and begins to glow.
• Flashlights are battery powered, and use smaller filament bulbs.
➢ Compact fluorescent lamps (CFLs):
• These give out the same amount of light as filament bulbs, for
one fifth the amount of electric power consumption.
• They last almost twelve times longer.
• Even though they are more expensive, they are good value for
money.
• They are more energy efficient.
➢ Light emitting diode (LED):
• LEDs are used in flashlights, bicycle lamps, string lights, even in
tube lights, solar-powered garden lights and street lights.
• They are the most efficient in converting electrical energy to
light energy.
5. Both the fuse and circuit breakers are used for breaking the close circuit in order to cut the current flow during power overload.
• The dissimilarity is that after overload we have to replace with a new fuse whereas circuit breakers simply have to flip the switch back again.
• Circuit breakers are more convenient to use.
6. Electromagnets are used in many scientific instruments.
• They are also used to store information on the computer’s hard
drive.
• Heavy loads are lifted by cranes using electromagnets.
• They are part of objects we use daily, such as a doorbell.
• Many household devices such as mixers, fridges, washing
machines need motors to run and these use electromagnets.