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

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 connecting electrical components allows electric current to flow. This arrangement is known as an electric circuit.

Q4: A fuse is connected with a live wire or with a neutral wire?

Ans:  The fuse is always connected with a live wire.

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

Ans:  Battery

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 a battery is

a.

b.

c.

d. None of These

Ans:  C

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

Ans:  Symbol of Electric bulb

Q11: Which one of the two minimises wastage of electricity, CFLs or an electric bulb?

Ans:  CFLs use less electricity to produce the same amount of light.

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 the 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 the 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 CFLs?

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

Ans:  Positive

Q22: Name a safety device in a 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 the current is switched ‘on’ in a room heater?

Ans:  It becomes red hot and gives out heat

Q27: Give the factors that affect the strength of the magnetic field at a point due to a straight conductor carrying current.

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

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

Ans:  No, the bulb will not glow when the switch is "OFF" because there is no closed circuit for current to flow.

Q29: What is a circuit diagram?

Ans:  A circuit diagram is a simplified representation of an electrical circuit using symbols to depict various components

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

Ans:  True

Q31: How can a solenoid be used to magnetise a steel bar?

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

Q32: Why do we use copper wires in electrical circuits?
Ans: Copper is a good conductor of electricity, which allows the current to flow easily through the wires.

Q33: A current through a horizontal power line flows in a north to south direction. What is the direction of the 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 can we show that a magnetic field exists around a wire carrying current?

Ans:  By using a magnetic compass which shows deflection.