Lesson Plan of Effects of Electric Current (Heating, Chemical & Magnetic Effects)
General Science Grade VII
Students’ Learning Outcomes
· Explain the effects of electric current in daily use appliances.
Information for Teacher
· The friction offered by a conductor, is called resistance.
· Different materials offer different amount of resistance.
· More is the resistance, more will be the heat produced in a conductor.
· Some materials give of heat and light when current flows through them (bulb, heater etc.)
· A magnetic effect is produced due to passage of current.
· Such magnets are called electromagnets.
· Electromagnets are used extensively in telephone, radio, television, telegraph, electric bell etc.
· When current is allowed to pass in electric cell, lead accumulator etc. Electric energy is converted into chemical energy (e.g. charging cells), but when the cells are used as a source of electric current then the chemical energy changes into electric energy.
· Chemical effect of an electric current: when an electric current passed through a liquid it may cause a chemical reaction to occur in the liquid-electrolysis
· Heat and light effect: when an electric current flows through the filament of light bulb, electric energy is converted into light and heat:
Concept Map
Material / Resources
Electric heater, magnet, cell/battery, conducting wire wrapped over iron nail, compass needle and steel paper clips
Worm up activity
Q. What makes electric iron hot?
(Expected response: Electric current)
Q. What makes electromagnet acts as a magnet?
(Expected response: Electric current)
· Today we will learn about the effects of electric current.
Development
Activity 1
· Divide the students into groups and ask to make a list of at least five home appliances in which electricity is used.
Q. why do we use electric heater?
(Expected response: To produce heat)
Q. How does electric heater work?
(Expected response: Electrical energy into heat energy)
Q. Why electric current produces heat in an electric heater?
(Expected response: The heater’s element offers a hindrance/friction in the passage
Of current, which is converted into heat)?
· Arrange an electric heater for activity in the class.
Activity 2
· Divide the students in groups. Ask the students to get the necessary apparatus i.e. beaker, oil/water, battery, key & connecting wires. Ask them to take 50ml of mustard oil in a beaker. Make a coil of Chrome wire. Connect the coil with a battery using connecting wires and a switch as shown in figure.
·
· Dip the coil in the oil. Also suspend a thermometer in the oil & note the temperature. Close the circuit. Observe the temperature after 10 minute and complete the table:
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Temperature before the current is passed
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Temperature after the current is passed
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Observation
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Inference
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Expected Response:
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Temperature before the current is passed
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Temperature after the current is passed
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Observation
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Inference
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May be 10 C
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May be 13 C
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Current has increased the temperature
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Electric current has converted into heat.
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Activity 3
· Provide a bar magnet, compass, battery/cell, wire wrapped around an iron nail and steel paper clips.
Q. If we bring a bar magnet near the paper pins what will happen?
(Expected response: Attracted by the magnet)
Q. Wrap the insulated wire around a nail. Connect the two ends of the wire with a battery.
What happens by bringing the nail near the steel paper clips?
(Expected response: Bring the nail near the steel paper clips. Steel paper clips cling to
The iron nail. The nail changes into a magnet when current flows through the wire
Wrapped around the nail. Remove the wire from the battery. The paper clips fall down).
Q. Why the coil becomes an electromagnet?
(Expected response: Due to electric current)
Q. What happens or removing the cell from the coil?
(Expected response: will not attract the paper clips)
Q. Why it doesn’t attract the paper clips on removing the cell?
(Expected response: it no longer remains a magnet)
Activity 4
· Provided required material to the students: A cardboard, insulated copper wire, key, dry cell and connecting wires. Pass the copper wire through the middle of the cardboard and connect its ends with the battery. Place a compass needle on the cardboard. Discuss the students as:
Q. What do you observe on completing the circuit?
(Expected response: there is some deflection in the compass needle)
Q. Why compass needle is deflected?
(Expected response: Magnet field has been produced)s
Q. What is your conclusion after passing the current through copper wire, which
Produces the deflection in compass needle?
(Expected response: magnetic effect has produced due to the passage of current
Through a conductor)
Sum up / Conclusion
· Conclude the lesson by asking the following questions:
Q. What makes the iron nail magnet?
(Expected response: Electric current, when current is passing through a coil it acts like
A magnet)
Q. What makes the electric heater heat up?
(Electric current, when current is passing through an electric heater it heats up due
To high resistance)
Q. How a battery is charged?
(Expected response: Electric energy is converted into chemical energy)
Follow up
· List at least three appliances in which you can observe the magnetic effects of current.
