CBSE CLASS 7 CHAPTER -ELECTRIC CURRENT AND ITS EFFECT -Q/A

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Q1: What is electric current   ?

 

   

Answer: An electric current is a flow of electric charge. This electric charge is carried by moving electrons(charge carriers) in a wire.

 

 

Q2:  What is electric circuit?

 

   

Answer:   An electric circuit is a path in which electrons (or current) flow.

 

 

Q3:  What is  different types of electric circuits  ?

 

   

Answer: There are two kind of electric circuit. 1. Closed circuit and 2. Open circuit 

 

 

Q4:  What is  closed circuit ?

 

   

Answer: Closed circuit   is complete circuit and  provide a continuous path for current flow throughout  the circuit.

 

 

Q5: What is  open circuit

 

   

Answer:    If the circuit is incomplete or broken, the  electric current doesn't flow. This type of circuit is called an Open Circuit. 

 

 

Q6:  Which device is used to make a circuit open .

 

   

Answer:  Electric switch

 

 

Q7:  What is cause of not glowing the electric bulb ?

 

   

Answer:   The circuit of electric bulb is open.

 

 

Q8: Does current flow in a closed circuit? 

 

 

Answer:  Yes    

 

 

Q9:  Why do circuits need to be closed?

 

   

Answer:  Closed circuit provide continuous path for electric current  to flow. 

 

 

Q10:  Which way does current flow in a closed circuit? . ?

 

   

Answer:    The current  flow in the external circuit  from the positive terminal and toward the negative terminal of the battery. While inside the battery it is opposite.

 

 

Q11: What are the four  requirements of a circuit?

 

   

Answer: 1. Source of electrical energy or battery 2. Connective wires 3. Load such as electr bulb or heating coil and 4. switch to control the current in circuit.

 

 

Q12: What are the effects of electric current?

 

   

Answer: The two effects of electric current are: 1. Heating effect and  2. Magnetic effect

 

 

Q13:What is heating effect of current ?

 

   

Answer:  When an electric current passes through a conductor .the conductor becomes hot after some time and produces heat. This is called heating effect of Electric Current. 

 

 

Q14:  .What causes the heating effect in electricity?

 

   

Answer: The resistance of conducting wire in the circuit opposes the flow of charge or electric current in circuit .Which creates heat  in conducting wire.

 

 

Q15:   Give examples heating effect of electric current ?

 

   

Answer: Electric iron, electric toaster, water heaters, etc., work on this effect .

 

 

Q16:   Which material is used for heating  element or coil of heater  ?

 

   

Answer: Nichrome

 

 

Q17:   What is Nichrome ?

 

   

Answer: Nichrome is an alloy of Nickel (80%) and Chromium (20%) and it has high resistance and high melting .This property  is suitable for making it as coil of heater.

 

 

Q18:  What is the magnetic effect of electric current ?

 

   

Answer:   When an electric current passes through a conducting wire , it behaves like a magnet. This magnetic effect of electric current is known as electromagnetic effect.   

 

 

Q19:  What is the applications of magnetic effect of current?  ?

 

   

Answer:   The magnetic effect of current is used in making electromagnets, electric bells, telephone instruments, electric fans, electric motors, loudspeakers and toys etc .

 

 

Q20:  What is the use of electric fuse?

 

   

Answer: Electric fuse is a safety device used to limit the current in an electric circuit which melts and breaks the circuit whenever there is an excess flow of current through the circuit. This prevent the fire in circuit. It is made up of  material having low melting point. Generally Fuse wire is made of alloy of lead and tin having low melting point of 200°C. 

 

Q21:Name the deivce which is used to 'make' or 'break' an electric circuit?

Answer: Switch

Q22:Which part of an electric circuit diagram is represented by straight lines?

Answer: Wire

Q23:Which electrical componenet is represnted by a symbol having two parallel lines: one long and thin, and the other short and thick?

Answer: Electric cell

Q24:State any two effects produced by electric current.

Answer: 1) Heating effect and 2) Magnetic effect

Q25:Which effect of electric current is utilised: (a)in an electric iron? (b)in an electric bulb?

Answer: (a)Heating effect & (b)Heating effect

Q26:Name the alloy which is used to make the heating elements of electrical heating appliances like an electric iron.

Answer: Nichrome

Q27:Name the metal which is used to make the filament of an electric bulb?

Answer: Tungsten

Q28:Which effect of current is utilised in the working of an electric fuse?

Answer:The heating effect

Q29:What is the full form of CFL?

Answer:Compact fluorescent lamps

Q30:Name the device which is being used increasingly in place of fuse?

Answer:MCB(Miniature circuit breaker)

Q31:Which important discovery was made by Oersted?

Answer: Magnetic effect of electricity

Q32:Name the scientisit who discovered magnetic effect of current?

Answer: Hans Christian orsted

Q33:In an electromagnet, which of the two really becomes a magnet: the piece and connected to an electric cell?

Answer: The peace of iron

Q34: Name any two devices in which electromagnets are used?

Answer: Electric bell and telephone.

Q35:What is the common name of the magnet made by using current?

Answer: Eletromagnet

Q36:Which of the following material is used for making electromagnet? Iron or Steel

Answer: Iron

Q37:Which effect of electric current is utilised in an electric bell?

Answer: Magnetic effect of electricity.

Q38: which effect of electric current is utilized in making electromagnets?

Answer: Heating effect of electricity.

Q39: A car battery is just one big cell? True/False

Answer: False

Q40:An electromagent is a temporary magnet?

Answer: True