Class 7 Science Chapter 10 Question Answers - Electric Current and Its Effects

Very Short Q&A:

Q1: Circuit diagram is a simplified conventional pictorial representation of an_______________.

Ans : electrical circuit

Q2: A circuit diagram uses standard symbols for electric components. True/ False.

Ans : True.

Q3: Define electric circuit.

Ans : A closed path formed by the interconnection of electrical components through which electric current flows is called an electrical circuit.

Q4: For a bulb to glow, it must be connected to a battery. Why?

Ans : because a bulb will require more power

Q5: What is a cell holder?

Ans : A compartment that holds two or more cells together to form a battery is called a cell holder.

Q6: If current does not flow through a circuit, then it is said to be an

1. Open circuit
2. Closed circuit
3. Incomplete circuit
4. Both a and c

Ans : Both a and c

Q7: A circuit is said to be open circuit or complete when current flows through it.. True/ False.

Ans : False

Q8: What is a battery?

Ans : A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another.

Q9: The symbol for battery is

Ans :  C

Q10: Draw the symbol for electric bulb in an electric circuit.

Ans : 

Q11: Which one of the two minimise wastage of electricity CFL’s or an electric bulb?

Ans : CFL’s

Q12: Enlist some appliances that work on the property of the heating effect of electric current.

Ans : the electric room heater, electric roti maker, electric iron, toaster, hair dryer, electric stove, immersion water heater, food warmer, electric coffee maker, electric rice cooker and geyser.

Q13: Electric room heaters have coils of wire that produce heat, which are known as heating elements.True/False.

Ans : True

Q14: State some factors that affect production of heat in a wire through which an electric current is passing.

Ans : Length and thickness of the wire, the duration of flow of current, and the material of the wire.

Q15: Name the principle of working of electric fuse.

Ans : The electric fuse works on the principle of the heating effect of electric current.

Q16: What is an electric fuse?

Ans : An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it.

Q17: What is the full form of MCB?

Ans : Miniature Circuit Breakers

Q18: What is the full form of CFL’s?

Ans : Compact Fluorescent Lamps

Q19: State one advantage of MCB.

Ans : These switches turn off automatically when there is an overload or a short circuit.

Q20: An electromagnet does not attract a piece of iron. True/ False

Ans : False

Q21: Longer line in the symbol for a cell represents its ------- terminal.

1. Negative
2. Positive
3. Neutral
4. None of these

Ans : Positive

Q22: Name a safety device in domestic circuit used to prevent electrical fire due to short circuit or overloading.

Ans : Electric fuse.

Q23: Enlist some appliances that work on the property of the magnetic effect of electric current.

Ans : Electric Bell, Motor, Fan etc.

Q24: What is meant by electric current?

Ans : Electric Current: Flow of electrons.

Q25: What is an electric circuit?

Ans : Electric Circuit : The closed path in which electric current flows

Q26: What happens when current is switched ‘on’ in a room heater?

Ans : It becomes red hot and gives out heat

Q27: Which of the two absorbs more radiation- a dark coloured object or a light coloured object?

Ans : Heating effect of electric current and magnetic effect of electric current.

Q28: Would any of the bulbs glow when the switch is in the ‘OFF’ position in a circuit?

Ans : In an electrical Circuit when we replace electrical components with their symbols we call it Circuit diagram.

Q29: What is a circuit diagram?

Ans : In an electrical Circuit when we replace electrical components with their symbols we call it Circuit diagram.

Q30: When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. True/False

Ans : True

Q31: The combination of two or more cells is called a __________________.

Ans : Battery

Q32: A straight wire carrying electric current is moving out of plane of paper and is perpendicular to it. What is the direction and type of induced magnetic field?

Ans : Induced magnetic field will be in the form of concentric circles in the plane of paper.

Q33: A current through a horizontal power line flows in north to south direction. What is the direction of magnetic field (i)at a point directly below it and (ii)at a point directly above it?

Ans : (i) West to East (ii) East to West

Q34: What do you mean by electromagnetic induction?

Ans : The process, due to which a changing magnetic field in a conductor induces a current in another conductor, is called electromagnetic induction.

Q35: How we can show that magnetic field exist around a wire carrying current?

Ans : By using magnetic compass which shows deflection.

Q36: How can a solenoid be used to magnetise a steel bar?

Ans : By inserting the steel bar inside the solenoid and switching on electric current.

Q37: Give the factors that affect strength of magnetic field at a point due to a straight conductor carrying current.

Ans : Magnitude of electric current, perpendicular distance between that point and conductor.

Q38: A fuse is connected with a live wire or with neutral wire?

Ans : Fuse is always connected with live wire.