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The MCQs below are drawn from the Physics subject category.
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14761
Assertion (A): Metallic-bodied appliances require three-pin plugs, whereas electric bulbs typically use two-pin connections. Reason (R): Three-pin connections are designed to reduce the heating of connecting wires.
The assertion is true because the third pin provides a ground connection for safety in metallic appliances. However, the reason is false; the third pin is for earthing to prevent electric shocks, not for reducing wire heating. The heating of wires is determined by current and resistance, not the number of pins.
14762
Convert 200 units of electrical energy into joules.
One unit of electrical energy is equal to 1 kilowatt-hour (kWh). Since 1 kWh = 1000 W * 3600 s = 3.6 × 10^6 Joules, 200 units = 200 * 3.6 × 10^6 J = 720 × 10^6 J, which is equivalent to 7.2 × 10^8 Joules.
14763
What materials are typically used to manufacture a fuse wire?
A fuse wire is typically made from an alloy of tin and lead. This specific alloy is chosen because it has a relatively low melting point and high resistance. This ensures that the wire will melt quickly when the current exceeds the rated capacity, effectively breaking the circuit to prevent damage.
14764
Which material is typically utilized for the heating element in an electric heater?
Nichrome is an alloy of nickel and chromium commonly used in heating elements because it has high electrical resistance and does not oxidize or melt at the high temperatures produced during operation.
14765
Calculate the daily energy consumption in units (kWh) for a 100 W electric bulb operating for 8 hours per day.
Energy consumption is calculated by multiplying power in kilowatts (kW) by time in hours (h). Since 100 W equals 0.1 kW, the energy used in 8 hours is 0.1 kW * 8 h = 0.8 kWh. In utility terms, 1 kWh is equivalent to 1 unit of electricity.
14766
Which physical effect of electric current is the operation of an electrical fuse based upon?
An electrical fuse is a safety device that utilizes the heating effect of current (Joule heating). When the current exceeds a safe limit, the heat generated causes the fuse wire to melt, thereby breaking the circuit and preventing damage to appliances.
14767
Which of the following statements regarding electrical components and safety is incorrect?
In standard electrical wiring color codes, the green or green-yellow wire is designated as the earth or ground wire for safety, not the live wire. The live wire is typically brown or red.
14768
According to standard electrical wiring color codes, which color is typically used to identify the neutral wire?
In many international electrical standards (such as IEC), the neutral wire is identified by blue insulation. In older or specific regional systems, black has also been used for neutral, making option C the standard choice.
14769
What form of energy is dissipated when a potential difference is applied across the ends of a conductor?
When a potential difference is maintained across a conductor, current flows through it. Due to the resistance of the material, collisions between electrons and the lattice structure convert electrical energy into thermal energy (Joule heating). Thus, electrical energy is the form being consumed or dissipated.
14770
Which metal is commonly utilized as the filament in incandescent light bulbs due to its high melting point?
Tungsten is used for light bulb filaments because it has an extremely high melting point (approximately 3422°C), allowing it to glow white-hot without melting when an electric current passes through it.
