1Which of the following units may NOT be used as a measure of power transfer?Joules per second (J/s)Kilowatts (kW)Watts (W)Watts per second (W/s)2A filament bulb is labelled ‘2.5 V, 1.25 W’.  How much energy will be transferred to it when it is connected to a 2.5 V battery for one minute?2.5 J150 J75 J48 J3The power adaptor of a laptop charges a laptop battery at a potential difference of 20 V and a current of 4 A.  Calculate its power output.24 W80 W5 W0.2 W4An electric motor is connected to a power supply.  The potential difference across the motor is 12 V and the current flowing through it is 2 A.  How much energy is transferred to the motor in 30 seconds?180 J24 J720 J12 J5Electrical energy is dissipated from a high voltage power cable at a rate of 50 kW.  If the current flowing in the cable is 100 A, calculate its resistance.0.005 Ω5,000,000 Ω500 Ω5 Ω6Calculate the amount of energy which is transferred when a charge of 72 C flows through a 6 V battery.0.08 J12 J78 J432 J

The unit that may NOT be used as a measure of power transfer is Watts per second (W/s). Power is the rate of energy transfer or conversion, with respect to time, and its SI unit is the Watt (W), which is equal to one Joule per second (J/s). Kilowatts (kW) is also a valid unit for measuring power, being equal to 1000 Watts. Watts per second (W/s), however, is not a valid unit for power, as it implies a rate of change of power, not power itself.

The energy transferred to a 2.5 V, 1.25 W filament bulb connected to a 2.5 V battery for one minute can be calculated using the formula for power: Power = Energy / Time. Rearranging for Energy gives: Energy = Power x Time. Substituting the given values gives: Energy = 1.25 W x 60 s = 75 Joules. So, the correct answer is 75 J.

The power output of a laptop power adaptor charging a laptop battery at a potential difference of 20 V and a current of 4 A can be calculated using the formula for power: Power = Voltage x Current. Substituting the given values gives: Power = 20 V x 4 A = 80 Watts. So, the correct answer is 80 W.

The energy transferred to an electric motor connected to a power supply, with a potential difference across the motor of 12 V and a current flowing through it of 2 A, in 30 seconds can be calculated using the formula for power: Power = Voltage x Current, and the formula for energy: Energy = Power x Time. Substituting the given values gives: Power = 12 V x 2 A = 24 W, and Energy = 24 W x 30 s = 720 Joules. So, the correct answer is 720 J.

The resistance of a high voltage power cable, with electrical energy being dissipated from it at a rate of 50 kW and a current flowing in it of 100 A, can be calculated using Ohm's law: Voltage = Current x Resistance, and the formula for power: Power = Voltage x Current. Rearranging for Resistance gives: Resistance = Voltage / Current. Substituting the given values gives: Power = 50 kW = 50000 W, Voltage = Power / Current = 50000 W / 100 A = 500 V, and Resistance = Voltage / Current = 500 V / 100 A = 5 Ohms. So, the correct answer is 5 Ω.

The amount of energy transferred when a charge of 72 C flows through a 6 V battery can be calculated using the formula for electrical energy: Energy = Charge x Voltage. Substituting the given values gives: Energy = 72 C x 6 V = 432 Joules. So, the correct answer is 432 J.