Electrical current passing through the human body can cause severe physiological damage. While the threshold for pain is lower, currents in the range of 50 mA to 100 mA are widely recognized as being potentially fatal, as they can induce ventricular fibrillation in the heart. The severity depends on the path of the current and the duration of exposure, but 50 mA is a significant danger threshold.

Energy in units (kWh) is calculated by multiplying power in kilowatts by time in hours. Power = 120 W = 0.12 kW. Time = 8 hours. Energy = 0.12 kW * 8 h = 0.96 kWh, which equals 0.96 units.

The grey deposit is actually caused by the sublimation of the tungsten filament. As the filament heats up, tungsten atoms evaporate and then deposit on the cooler inner surface of the glass bulb. While the provided answer suggests dust, the physical phenomenon is tungsten deposition.

Electrical energy is the product of power and time. While the watt and kilowatt are units of power (the rate of energy usage), the kilowatt-hour (kWh) is a unit of energy. It represents the total energy consumed by a device with a power rating of one kilowatt operating for one hour.

A kilowatt-hour (kWh) is a unit of energy, not power. It represents the amount of energy consumed by a device with a power rating of one kilowatt (1000 watts) operating continuously for a duration of one hour. It is commonly used as a billing unit for electrical energy consumption by utility companies, as it provides a convenient scale for measuring the energy used in homes and businesses.

Assertion (A) is true because current flow causes heating (Joule heating). However, Reason (R) is false because the heat is generated by the collision of moving electrons with the lattice ions (atoms) of the metal, not by the collision of metal atoms with each other.

A fuse wire is designed to melt and break the circuit when excessive current flows. It requires a material with a low melting point and high resistance. An alloy of tin and lead (solder) is commonly used because it has a relatively low melting point compared to pure copper or other metals, ensuring the fuse acts as a safety device during overcurrent conditions.

Electricity is transmitted at high voltages to minimize energy loss due to resistance in the transmission lines. According to Joule's Law, power loss in a conductor is proportional to the square of the current (P = I^2R). By increasing the voltage, the current required to transmit the same amount of power is significantly reduced, thereby decreasing the heat energy dissipated as waste.

According to Joule's Law of Heating, H = I^2Rt. Since the current (I) and time (t) are constant, heat is directly proportional to resistance (R). A thin wire has a smaller cross-sectional area, resulting in higher electrical resistance compared to a thick wire. Consequently, the thin wire dissipates more heat energy due to the increased resistance encountered by the flowing electrons.

A dry cell is a type of electrochemical cell. It functions by facilitating chemical reactions between its internal components (anode, cathode, and electrolyte), which release electrons and convert stored chemical potential energy into electrical energy for use in a circuit.