Short answer type questions
1 Name any four components of an electric circuit. Give their electrical symbols.
2 Draw a circuit diagram where an electric current will flow. Add a component that will
help open and close the circuit and label it.
3 Explain 'heating effect of electric current'.
4 What is 'magnetic effect of electric current?
5 What is the purpose of having an electromagnet in an electric bell?
Answers
Answer:
Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position, and battery?
Answer:
Connecting wires
Physics Class 7 Electric Currents Connecting Wires
2. Switch in “ON” position
Physics Class 7 Electric Currents Switch ON
3. Electric Bulb
Physics Class 7 Electric Current Bulb
4. Electric Cell
Physics Class 7 Electric Current Electric Cell
5. Switch in “OFF” position
Physics Class 7 ELectric Current Switch OFF
6. Battery
Physics Class 7 Electric Currents Battery
Question2.
Draw the circuit diagram to represent the circuit shown in Fig?
Physics Class 7 Electric Circuits Electric Circuit 5
Answer:
In the above circuit one end of the bulb is connected to the battery and another end to the safety pin.
But the other end of the battery is not connected to the safety pin. Therefore there will be no flow of current as the switch is in “OFF” position.
This shows the circuit is not complete.
Circuit diagram of the above electric circuit will be:
Physics Class 7 Electric Circuits Electric Circuit 4
Question 3.
The given figure shows four cells fixed on a board.
Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
Physics Class 7 Electric Circuits InCorrect Connections
Answer:
In order to make battery, the positive terminal (+) of one cell should be connected to the (-) terminal of another cell and so on.
Physics Class 7 Electric Currents Battery With Correct Connections
Question 4.
The bulb in the circuit shown in figure does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
Physics Class 7 ElectricCircuits CIrcuit 3
Answer:
The positive terminal (+) of one cell should always be connected to negative terminal (-) of another cell.
But in case of above circuit both the positive terminals are connected to each other. This is the reason battery is not able to generate electricity.
Therefore the change which should be made to the circuit will be that the positive terminal (+) should be connected to negative terminal (-) of the cell and vice-versa.
Physics Class 7 Electric Circuits Circuit 2
Question 5.
Name any two effects of electric current.
Answer:
The two effects of electric current are:-
Heating effect
Magnetic effect
Heating Effect of current: When an electric current passes through a wire, the wire gets heated. This is known as the heating effect of current.
The heating effect is used in many heating applications like electric heater, electric iron, light bulb etc.
Magnetic Effect of current: When an electric current flows through a wire, it generates magnetic field around it.
This effect is known as magnetic effect of current. Magnetic Effect of electric current has many applications like power lift, electric bell, electric fan etc.
Physics Class 7 Electric Currents Magnetic & Electric Effects
Question 6.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
Answer:
The current flowing through the conducting wire creates magnetic field. When a compass is kept nearby this wire,
it will experience two magnetic fields (one magnetic field due to wire and another magnetic field due to compass).
As a result when they interact with each other there will be deflection seen in the magnetic needle.
When the current is switched off, there is no magnetic field produced by the wire, magnetic needle does not deflect from its north-south position.
Physics Class 7 ElectricCircuits Magnetic Needle
Question 7.
Will the compass needle show deflection when the switch in the circuit shown by Figure is closed?
Physics Class 7 Electric Currents Circuit With Compass
Answer:
There is no source of electric current i.e. (battery or cell). The circuit is an open circuit.
There will be no current flowing it, as a result, there will be no magnetic field produced by the wires.
Therefore there is no deflection shown by the compass needle.
Question 8.
Fill in the blanks:
(a) Longer line in the symbol for a cell represents its _________terminal.
(b) The combination of two or more cells is called a _________.
(c) When current is switched ‘on’ in a room heater, it ________.
(d) The safety device based on the heating effect of electric current is called a ___________.
Answer:
Longer line in the symbol for a cell represents its Positive
Physics Class 7 Electric Currents Electric Circuit With Battery1
The combination of two or more cells is called a Battery.
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Answer:
1)Inductor Inductor Circuit Symbol
Motor Motor Circuit Symbol
Bell Bell Circuit Symbol
Buzzer Buzzer Circuit Symbol
3)When current flows through a conductor, heat energy is generated in the conductor. The heating effect of an electric current depends on three factors: The resistance, R of the conductor. A higher resistance produces more heat. ... The longer the time the larger the amount of heat produced.
4)Magnetic Effect of current of Electromagnetism. The term "magnetic effects of current " means that " a current flowing in a wire produces a magnetic field round it ". the magnetic effect of current was discovered by Oersted found that a wire carrying a current was able to deflect a magnetic needle.
5)An electric powered bell is a mechanical bell that purposes by using ability of an electromagnet. whilst the swap is pushed 'on', modern-day flows in the time of the coil. The coil turns into an electromagnet, attracting the metallic strip. This strikes the clanger to hit the bell, yet additionally breaks the circuit.