Question

a) A car has a fresh storage battery of EMF 12V, internal resistance 5.0 x 10 ^-2 W. If the starter motor draws a current of 90 A, what is the terminal voltage of the battery when the starter is on? (b) After a long use, the internal resistance of the storage battery increases to 500W. What maximum current can be drawn from the battery? Assume EMF of the battery to remain unchanged.

Answer 1

a) A car has a fresh storage battery of EMF 12V, internal resistance 5.0 x 10 ^-2 W.

If the starter motor draws a current of 90 A, The terminal voltage of the battery when the starter is on is 7.5 volts.

(b) After a long use, the internal resistance of the storage battery increases to 500W.

The maximum current can be drawn from the battery is 0.024 amps.

Answer 2

Answer:

we know

a.

V=E-Ir

=12-4.5=7.5V.

b.

the maximum current can be drawn when it is shorten i.e. V=0

therfore,

Imax=E÷r

=12÷500

=240mA.

c.

during the diacharge of the accumulator ,the current inside the cell is opposite to what it is when the accumulator diacharges .that is during the charging ,current flows from the +ve to -ve terminal inside the cell. consequently,during charging.

V=E+Ir.

hence V must be greater than 12V during charging.