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Q1. In domestic wiring, appliances are connected in:
In domestic wiring, appliances are connected in parallel so that each appliance gets the same voltage (220V) and can be operated independently. If one appliance fails or is switched off, others continue to work. This is the safest and most practical arrangement for household wiring.
Q2. A current-carrying conductor produces a:
A current-carrying conductor produces a magnetic field around it. This is the magnetic effect of electric current, discovered by Oersted. The magnetic field lines form concentric circles around the conductor.
Q3. Fuse protects appliances by:
A fuse protects appliances by breaking the circuit when excess current flows. The fuse wire melts due to the heating effect of current and breaks the connection, stopping the flow of current and preventing damage to appliances.
Q4. The earth wire is connected to:
The earth wire is connected to a metal plate buried deep in the earth. This provides a low-resistance path for leakage current to flow safely into the ground, preventing electric shocks and ensuring safety.
Q5. In an AC generator, the induced current changes direction once in each:
In an AC generator, the induced current changes direction once in each half revolution (180°) of the coil. This is because the coil’s orientation relative to the magnetic field changes, and the direction of induced current reverses.
Q6. The magnetic field near a long straight wire consists of:
The magnetic field near a long straight current-carrying wire consists of concentric circles centred on the wire. The circles are in a plane perpendicular to the wire, and the direction is given by the right-hand thumb rule.
Q7. Fleming’s left-hand rule gives the direction of:
Fleming’s left-hand rule gives the direction of the force on a current-carrying conductor placed in a magnetic field. The thumb gives the direction of force, the forefinger gives the magnetic field direction, and the middle finger gives the current direction.
Q8. Bulbs and fans are usually connected to a circuit of rating:
Bulbs and fans are usually connected to a circuit rated at 5 A. This is sufficient for low-power appliances like lights and fans. High-power appliances like geysers and air conditioners use 15 A circuits.
Q9. The green insulated wire in domestic wiring is the:
The green insulated wire (or green with yellow stripes) in domestic wiring is the earth wire. It provides a safety path for leakage current to flow to the ground, protecting users from electric shocks.
Q10. Short-circuiting causes current to:
Short-circuiting causes current to increase abruptly because the live and neutral wires come into direct contact, bypassing the resistance of the appliances. This sudden increase in current can cause damage and fire. Fuses protect against this.
Q11. Magnetic field lines around a straight current-carrying wire are:
Magnetic field lines around a straight current-carrying wire are concentric circles. The lines are centred on the wire and lie in planes perpendicular to the wire. This pattern was first demonstrated using iron filings.
Q12. Electric motor works on the principle of:
An electric motor works on the principle of force on a current-carrying conductor placed in a magnetic field. The force causes the coil to rotate, converting electrical energy into mechanical energy.
Q13. Magnetic field exists in the region:
A magnetic field exists in the region surrounding a magnet. This is the area where the magnetic force can be detected. The field extends from the north pole to the south pole outside the magnet.
Q14. Short-circuiting occurs when live wire and neutral wire:
Short-circuiting occurs when the live wire and the neutral wire touch directly (or come into contact through a low-resistance path). This bypasses the appliances, causing a very large current to flow, which can damage the circuit.
Q15. Each appliance in a house has a separate switch so that it can be:
Each appliance in a house has a separate switch so that it can be turned ON or OFF independently. This allows individual control of each appliance without affecting others. This is possible because appliances are connected in parallel.
Q16. The main purpose of the earth wire is to:
The main purpose of the earth wire is to provide safety from electric shock. If a fault occurs and the metal body of an appliance becomes live, the earth wire provides a low-resistance path for the current to flow to the ground, preventing electric shock.
Q17. A compass needle is actually a small:
A compass needle is actually a small bar magnet. It has a north pole and a south pole. It aligns itself with the Earth’s magnetic field, pointing north-south. This is how a compass is used to find direction.
Q18. Fuse is a safety device used to protect circuits from:
A fuse is a safety device used to protect circuits from short-circuiting and overloading. When excess current flows, the fuse wire melts and breaks the circuit, preventing damage to appliances and reducing the risk of fire.
Q19. A generator converts:
A generator converts mechanical energy into electrical energy. When a coil rotates in a magnetic field, an electric current is induced. This is based on the principle of electromagnetic induction.
Q20. Overloading can also be caused by:
Overloading can be caused by connecting many appliances to one socket or extension board. This draws more current than the circuit is designed for, causing overheating and potentially damaging the wiring or starting a fire.
Q21. High power appliances like geysers are connected to a circuit of rating:
High power appliances like geysers, air conditioners, and electric irons are connected to a circuit rated at 15 A. These appliances draw more current than low-power devices like bulbs and fans, which use 5 A circuits.
Q22. Earthing ensures that leakage current keeps the appliance body at the potential of:
Earthing ensures that leakage current keeps the appliance body at the potential of the Earth (zero potential). If the appliance body becomes live, the current flows safely to the ground, preventing electric shock.
Q23. Overloading may occur due to accidental hike in:
Overloading may occur due to an accidental hike in voltage supply. When the voltage increases, the current drawn by appliances also increases (I = V/R), which can exceed the safe limit and cause overloading.
Q24. The schematic diagram of a domestic circuit shows appliances connected:
The schematic diagram of a domestic circuit shows appliances connected in parallel. This is the standard wiring configuration for homes, ensuring each appliance gets the same voltage and can be operated independently.
Q25. A current-carrying conductor placed in a magnetic field experiences a:
A current-carrying conductor placed in a magnetic field experiences a force. This is the basis of the electric motor. The force is given by F = BIL sin θ and its direction is given by Fleming’s left-hand rule.
Q26. The potential difference between live and neutral wire in India is:
The potential difference between the live wire and the neutral wire in India is 220 V. This is the standard voltage supplied to homes for domestic use. In some countries, the voltage is 110 V or 240 V.
Q27. AC changes direction after every:
In India, AC has a frequency of 50 Hz, meaning it completes 50 cycles per second. One cycle consists of two changes of direction, so AC changes direction 100 times per second—once every 1/100 second.
Q28. Electric power supplied to homes is:
Electric power supplied to homes is AC (alternating current). AC is used because it can be easily transformed to higher or lower voltages, making it efficient for long-distance transmission. DC is not used for household supply in most countries.
Q29. Domestic electric supply reaches houses through:
Domestic electric supply reaches houses through overhead poles (in rural areas) or underground cables (in urban areas). The supply comes from the grid and is stepped down to 220 V by transformers before entering homes.
Q30. Electric power supplied to homes is called:
Electric power supplied to homes is called the main supply or mains. It is the AC power that comes from the electricity grid through transformers, distribution lines, and meters into household circuits.
Q31. An electromagnet consists of:
An electromagnet consists of a soft iron core with a coil of insulated wire wound around it. When current flows through the coil, the soft iron becomes magnetized. When the current stops, it loses its magnetism.
Q32. The direction of induced current is given by:
Fleming’s right-hand rule is used to determine the direction of induced current when a conductor moves in a magnetic field. The thumb points in the direction of motion, the forefinger in the direction of the magnetic field, and the middle finger gives the direction of induced current.
Q33. The wire with red insulation in domestic circuits is called:
The wire with red insulation (or brown) in domestic circuits is called the live wire. It carries the current from the mains supply to the appliances. It is at a potential of 220 V with respect to the neutral wire.
Q34. Appliances like electric press and refrigerator have metallic bodies mainly for:
Appliances like electric presses and refrigerators have metallic bodies mainly for safety through earthing. The metallic body is connected to the earth wire so that if a fault occurs, the current flows safely to the ground, preventing electric shock.
Q35. Magnetic field lines are closer together where the magnetic field is:
Magnetic field lines are closer together where the magnetic field is strong. The density of field lines indicates the strength of the magnetic field. Closer lines mean a stronger field, which is why the field is strongest at the poles.
Q36. The device used for producing electric current is a:
The device used for producing electric current is a generator. It converts mechanical energy into electrical energy through the principle of electromagnetic induction. A motor converts electrical energy into mechanical energy.
Q37. The direction of magnetic field around a straight wire is given by the:
The direction of the magnetic field around a straight current-carrying wire is given by the right-hand thumb rule. If the thumb points in the direction of current, the curled fingers give the direction of the magnetic field lines.
Q38. The frequency of AC supply in India is:
The frequency of AC supply in India is 50 Hz. This means the current changes direction 100 times per second (50 complete cycles per second). In the USA and some other countries, the frequency is 60 Hz.
Q39. A solenoid carrying current behaves like a:
A solenoid carrying current behaves like a bar magnet. One end of the solenoid behaves like a north pole, and the other end behaves like a south pole. The magnetic field inside the solenoid is uniform and parallel.
Q40. Electricity meter in a house is connected through a:
The electricity meter in a house is connected through a main fuse. The main fuse protects the entire house from overloading and short-circuiting. The meter measures the electrical energy consumed by the household.
Q41. Overloading in a circuit occurs when:
Overloading in a circuit occurs when excess current flows through the circuit. This can happen due to connecting too many appliances, short-circuiting, or a sudden voltage hike. The excess current can cause overheating and damage.
Q42. During short-circuiting, the current in the circuit:
During short-circuiting, the current in the circuit increases heavily because the live and neutral wires come into direct contact, bypassing the resistance of the appliances. This sudden increase can cause damage and fire.
Q43. Magnetic field lines are used to represent:
Magnetic field lines are used to represent the magnetic field. They show both the direction and strength of the field. The direction is shown by arrows, and the strength is indicated by the spacing of the lines.
Q44. The function of a fuse in domestic circuits is to:
The function of a fuse in domestic circuits is to prevent damage due to high current. When current exceeds the safe limit, the fuse wire melts and breaks the circuit, protecting appliances and reducing the risk of fire.
Q45. Parallel connection ensures that each appliance gets:
Parallel connection ensures that each appliance gets the same potential difference (voltage). In household wiring, all appliances are connected in parallel, so each receives the full 220 V supply. This is why all appliances work properly regardless of others being switched on or off.
Q46. The wire with black insulation in domestic circuits is called:
The wire with black (or light blue) insulation in domestic circuits is called the neutral wire. It completes the circuit and carries the return current. The neutral wire is at zero potential with respect to the earth.
Q47. Metallic bodies of appliances are connected to the earth wire to:
Metallic bodies of appliances are connected to the earth wire to provide a low-resistance path for leakage current to flow to the ground. This prevents the metallic body from becoming live and protects users from electric shock.
Q48. An electric motor converts:
An electric motor converts electrical energy into mechanical energy. The current-carrying coil experiences a force in a magnetic field, causing it to rotate. This rotation can be used to do mechanical work.
Q49. Electromagnetic induction refers to production of current due to:
Electromagnetic induction refers to the production of current due to a changing magnetic field. When the magnetic flux through a coil changes, an induced current is produced. This is the principle behind generators and transformers.
Q50. The fuse wire melts due to:
The fuse wire melts due to Joule’s heating effect (H = I²Rt). When excess current flows, the heat produced in the fuse wire increases and melts it, breaking the circuit. This protects the appliances from damage due to overcurrent.