What determines the rate at which energy is delivered by a current? An electric heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.

The rate of consumption of electric energy in an electric appliance is called electric power. Hence, the rate at which a current delivers energy is the power of the appliance. Given parameters: The resistance of the electric heater (R) = 8 Ω , Current drawn (I) = 15 A , Time = 2 hrs . T = 2 × 60 × 60 s Time (T) = 7200 s The rate of heat produced by the device in terms of power is expressed as P = I 2 R P = 15 × 15 × 8 P = 1800 W . Hence, the power developed in the heater is 1800 W .

Write the S.I. unit of resistivity. An electric motor takes 5 A from a 220 V source. Determine the power of the motor and energy consumed in 2 hours.

The SI unit of Resistivity is Ω m . The resistivity of a conductor is the resistance of the conductor that is 1 m long and 1 m 2 in a cross-sectional area. Given parameters, Voltage (V) = 220 V , Current (I) = 5 A , Time (t) = 2 h = 2 × 60 × 60 = 7200 s Power (P) is given by the expression, P = V × I P = 220 × 5 P = 1100 W Energy consumed by the motor = P × t P = 1100 × 7200 P = 7 . 92 × 10 6 J Therefore, the power of the motor = 1100 W Energy consumed by the motor = 7 . 92 × 10 6 J .

How electrical charges flow inside a wire. Explain.

Whenever we apply a potential difference across a wire an electric field is created in the wire. This electric field makes the free-electron move in the direction opposite to the electric field (this happens because the electron has a negative charge, So it moves in the opposite direction) with a speed called drift speed. As the field is from high potential to low potential, so free electrons in the wire move towards the higher potential. Hence, current flows from higher potential to lower potential (opposite to the flow of electrons); As the flow of electrons is the flow of current in opposite direction.

A current of 0 . 6 A is drawn by a filament of an electric bulb for 5 minutes. Find the amount of electric charge that flows through the circuit.

We know that Formula for Electric Current as I = Q t where Q = Charge measured in coulombs, I = Current in ampere, t = Time in which current is applied in seconds. I = Q t ⇒ Q = I t . Now putting the value in the formula, Q = ( 0 . 6 A ) × ( 5 × 60 ) s Q = 0 . 6 × 300 Q = 180 C .