Electricity: Magnetic and Heating Effects
Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.
Electric Circuit Components and Symbols
SubtopicElectric Circuit Components and Symbols under Electricity: Magnetic and Heating Effects for Grade 7 CBSE.
Preview questions (no answers)
- 1.
Which scientist first noticed the deflection of a magnetic compass needle when current passed through a nearby wire?
A.Newton
B.Hans Christian Oersted
C.Thomas Edison
D.Michael Faraday
- 2.
When electric current passes through a wire, it behaves like a magnet. This is known as the:
A.Heating effect
B.Electric effect
C.Magnetic effect
D.Frictional effect
- 3.
The safety device based on the heating effect of electric current is called a:
A.Switch
B.Fuse
C.Electromagnet
D.Cell
- 4.
Which effect of electric current is used in an electric heater?
A.Magnetic effect
B.Heating effect
C.Chemical effect
D.Lighting effect
- 5.
Which material is used for the filament of an electric bulb due to its high melting point?
A.Copper
B.Silver
C.Tungsten
D.Nichrome
- 6.
An electric bell works on the principle of:
A.Heating effect of current
B.Magnetic effect of current
C.Chemical effect of current
D.Static electricity
- 7.
What happens to a compass needle placed near a current-carrying wire if the direction of current is reversed?
A.It stops moving
B.It deflects in the opposite direction
C.It points only towards the North Pole
D.It spins continuously
- 8.
A student, Rahul, builds a circuit to test the magnetic effect of electric current. He notices that when the switch is closed, a magnetic compass placed near the wire deflects. However, he accidentally replaces a single cell with a battery of four cells in series, while keeping the rest of the components the same. According to the symbols in his schematic, what change would be observed in the circuit's behavior and the compass needle?
A.The compass needle will deflect more because the increased voltage increases the current, strengthening the magnetic field.
B.The compass needle will stop deflecting because the magnetic field only depends on the number of wire coils, not the number of cells.
C.The compass needle will deflect in the opposite direction because adding more cells reverses the polarity of the current.
D.The bulb in the circuit will glow dimmer because the extra cells increase the total resistance of the circuit.
- 9.
An electrician is installing a safety device in a house circuit to prevent fires caused by short-circuits. He needs to choose a component that will melt and break the circuit if the current exceeds a safe limit. Which symbol in the provided diagram represents this safety component, and where should it be placed relative to the appliance (lamp)?
A.The fuse symbol, placed in series before the lamp
B.The battery symbol, placed in parallel with the lamp
C.The resistor symbol, placed after the switch
D.The switch symbol, kept in the open position
- 10.
A technician is troubleshooting a faulty electric bell circuit. The bell rings continuously even when the soft iron strip is pulled away from the contact screw. Upon inspecting the circuit diagram, she realizes a component is represented incorrectly for a standard bell mechanism. Based on the symbols, which component's failure or incorrect placement would stop the 'make-and-break' movement required for the bell to function?
A.The electromagnet remaining magnetized because the switch is bypassed
B.The battery being replaced by a single piece of wire
C.The lamp being placed in parallel with the battery
D.The switch being placed in the 'OFF' position
Download the worksheet for Electricity: Magnetic and Heating Effects - Electric Circuit Components and Symbols to practice offline. It includes additional chapter-level practice questions.
Heating Effect of Electric Current and Fuses
SubtopicHeating Effect of Electric Current and Fuses under Electricity: Magnetic and Heating Effects for Grade 7 CBSE.
Preview questions (no answers)
- 1.
An MCB trips when:
A.The current is safe
B.The current exceeds the safe limit
C.The battery is fully charged
D.The light is turned on
- 2.
What ensures that an appliance is manufactured according to safety standards in India?
A.The color of the wire
B.The ISI mark
C.The size of the plug
D.The weight of the device
- 3.
Which appliance works on the same principle as the electric iron?
A.Electric bell
B.Electric heater
C.Electric motor
D.Television
- 4.
In an electric bulb, the energy conversion is:
A.Electrical to Sound
B.Electrical to Heat and Light
C.Chemical to Electrical
D.Magnetic to Heat
- 5.
When an electric current flows through a wire, the heat energy produced is proportional to . What does 'R' represent in this context?
A.Radiation
B.Resistance
C.Radius
D.Reactance
- 6.
If a fuse wire melts, the circuit becomes a/an ________ circuit.
A.Closed
B.Open
C.Parallel
D.Short
- 7.
Why should you never touch an illuminated electric bulb connected to the mains?
A.It might be slippery
B.It can be very hot and cause a burn
C.It will immediately turn off if touched
D.It contains poisonous gases that leak when touched
- 8.
If a circuit is overloaded, the primary danger is that:
A.The voltage will drop to zero.
B.The wires will heat up excessively and may start a fire.
C.The appliances will start working in reverse.
D.The magnetic field will become too strong and attract metal objects.
- 9.
The heating effect of electric current is used in which of the following?
A.Electric Bell
B.Telephone
C.Electric Room Heater
D.Electromagnet
- 10.
Why is it unsafe to use a fuse with a 'higher' current rating than specified for an appliance?
A.It will consume more power.
B.It will not blow even if a dangerously high current flows, leading to a fire.
C.It will blow too easily.
D.It will cause the appliance to run slower.
Download the worksheet for Electricity: Magnetic and Heating Effects - Heating Effect of Electric Current and Fuses to practice offline. It includes additional chapter-level practice questions.
Magnetic Effect of Electric Current
SubtopicMagnetic Effect of Electric Current under Electricity: Magnetic and Heating Effects for Grade 7 CBSE.
Preview questions (no answers)
- 1.
When making an electromagnet, the wire must be wound in the form of a:
A.Square
B.Coil
C.Straight line
D.Zig-zag
- 2.
In an electric bell, the circuit is broken at the:
A.Switch
B.Battery
C.Contact screw and iron strip
D.Electromagnet coil
- 3.
The magnetic effect of electric current is used in which of the following?
A.Electric heater
B.Electric toaster
C.Electric fan motor
D.Electric iron
- 4.
A crane using an electromagnet is better than one with a permanent magnet for moving scrap because:
A.It is cheaper
B.It can release the scrap easily by switching off current
C.It is much lighter
D.It doesn't use electricity
- 5.
Which of the following correctly describes the nature of an electromagnet's magnetism?
A.It is permanent and cannot be destroyed
B.It is present only as long as current flows
C.It depends on the temperature of the room
D.It only attracts non-metals
- 6.
The direction of the magnetic field around a straight current-carrying wire depends on:
A.The length of the wire
B.The direction of the current
C.The thickness of the wire
D.The type of insulation
- 7.
If you want to make an electromagnet that can pick up 50 paper clips instead of 10, what should you do?
A.Increase the amount of current from the battery
B.Use a plastic core
C.Use a shorter wire
D.Reverse the battery terminals
- 8.
The magnetic effect of electric current was first observed by which scientist?
A.Michael Faraday
B.Hans Christian Oersted
C.James Watt
D.Benjamin Franklin
- 9.
An electric bell is ringing. If the hammer is made of plastic instead of iron, what will happen?
A.The bell will work normally but make a different sound.
B.The bell will not ring because the hammer will not be attracted to the magnet.
C.The electromagnet will burn out.
D.The armature will move but the hammer will not strike the gong.
- 10.
A student is testing a magnetic compass near a vertical wire. She notices that when the current flows 'up', the North pole of the needle points West. What will happen if she keeps the current 'up' but moves the compass to the opposite side of the wire?
A.The North pole will still point West.
B.The North pole will now point East.
C.The North pole will point North.
D.The North pole will point South.
Download the worksheet for Electricity: Magnetic and Heating Effects - Magnetic Effect of Electric Current to practice offline. It includes additional chapter-level practice questions.
Electromagnets and Electric Bell
SubtopicElectromagnets and Electric Bell under Electricity: Magnetic and Heating Effects for Grade 7 CBSE.
Preview questions (no answers)
- 1.
If you increase the number of cells in a circuit containing an electromagnet, the magnetic strength will:
A.Decrease
B.Increase
C.Stay the same
D.Become zero
- 2.
The deflection of a compass needle by a current-carrying wire proves that the wire is acting like a:
A.Battery
B.Magnet
C.Resistor
D.Fuse
- 3.
Which of these is the most important component for making an electromagnet?
A.A glass rod
B.A coil of insulated wire
C.A plastic switch
D.A wooden base
- 4.
An electric fuse works on the principle that current produces:
A.Sound
B.Magnetism
C.Heat
D.Light
- 5.
In an electric bell, the continuous 'ring-ring' sound is produced because:
A.The hammer hits the gong and stays there
B.The circuit is made and broken repeatedly
C.The battery provides alternating current
D.The gong is vibrating on its own
- 6.
The magnetism of an electromagnet can be 'switched off'. This is because:
A.The core is made of a permanent magnet
B.The magnetic field is produced by the flow of electrons
C.The coil is made of rubber
D.The battery is always rechargeable
- 7.
Why is copper wire used for connecting circuits but not for the heating element of a toaster?
A.Copper is too expensive
B.Copper has very low resistance and doesn't get hot enough
C.Copper is a magnetic material
D.Copper melts at room temperature
- 8.
Why does the wire of a fuse need to have a lower melting point than the other wires in the house?
A.To ensure it melts first and breaks the circuit during excessive current.
B.To allow more current to flow through the circuit.
C.To prevent the fuse from getting too hot.
D.To save energy by reducing the total resistance.
- 9.
If the insulation of a heating element in an electric kettle breaks, what is the most immediate danger?
A.The kettle will stop heating.
B.The water will become radioactive.
C.An electric shock if the metal body of the kettle is touched.
D.The magnetic field will destroy nearby electronics.
- 10.
What is the function of the 'contact screw' in an electric bell?
A.To hold the gong in place.
B.To complete or break the circuit as the armature moves.
C.To increase the resistance of the circuit.
D.To change the direction of current flow.
Download the worksheet for Electricity: Magnetic and Heating Effects - Electromagnets and Electric Bell to practice offline. It includes additional chapter-level practice questions.