Electromotive Force: Calculate Charge, E.M.F & P.D.

[Xazdrubal]

Homework Statement

Atorch battery transfers 5200J of chemical energy into electrical energy while supplying a current of 0.25A for 4400 s. The bulb transfers 4800 j of electrical energy into heat and light during this time. Calculate
a)the charge that flows
b)the e.m.f. of the battery
c) the p.d. across the bulb
d)the lost volts

Homework Equations

Q=IT

The Attempt at a Solution

a) 0.25 x 4400 = 1100 C
b)5200/1100 = 4.73V
C) V=W/Q

NOT SURE WHAT TO DO FOR C / D /

 

[berkeman]

Homework Statement

Atorch battery transfers 5200J of chemical energy into electrical energy while supplying a current of 0.25A for 4400 s. The bulb transfers 4800 j of electrical energy into heat and light during this time. Calculate
a)the charge that flows
b)the e.m.f. of the battery
c) the p.d. across the bulb
d)the lost volts

Homework Equations

Q=IT

The Attempt at a Solution

a) 0.25 x 4400 = 1100 C
b)5200/1100 = 4.73V
C) V=W/Q

NOT SURE WHAT TO DO FOR C / D /

Welcome to the PF.

What does "p.d. across the bulb" mean? Power dissipated?

If so, then power is just total energy divided by time, right?

Once you have the bulb power, calculate the bulb voltage, and the difference between that and the battery source EMF is what is lost across the battery's internal resistance.

 

[kerimek]

c) The p.d. across the bulb can be calculated using Ohm's Law: V=IR, where V is voltage, I is current, and R is resistance. Since the bulb is transferring 4800 J of energy and has a current of 0.25A, the resistance can be calculated as R=V/I=4800/0.25= 19200 ohms. Therefore, the p.d. across the bulb is V=IR=0.25 x 19200= 4800V.

d) The lost volts can be calculated by subtracting the p.d. across the bulb from the e.m.f. of the battery: Lost volts = 4.73V - 4800V = -4795.27V. This means that there is a significant loss of voltage due to the resistance in the circuit, leading to a lower voltage across the bulb than the e.m.f. of the battery.