128 Basic Engineering Mathematics
9. The current i flowing in a capacitor at
time t is given by i = 12.5(1 − e −t /CR ),
where resistance R is 30 k and the
capacitance C is 20 μF. Determine (a)
the current flowing after 0.5 seconds and
(b) the time for the current to reach
10 amperes.
10. The amount A after n years of a sum invested
P is given by the compound interest law
A = Pe rn/100 , when the per unit interest rate
r is added continuously. Determine, correct
to the nearest pound, the amount after 8 years
for a sum of £1500 invested if the interest
rate is 6% per annum.
9. The current i flowing in a capacitor at
time t is given by i = 12.5(1 − e −t /CR ),
where resistance R is 30 k and the
capacitance C is 20 μF. Determine (a)
the current flowing after 0.5 seconds and
(b) the time for the current to reach
10 amperes.
10. The amount A after n years of a sum invested
P is given by the compound interest law
A = Pe rn/100 , when the per unit interest rate
r is added continuously. Determine, correct
to the nearest pound, the amount after 8 years
for a sum of £1500 invested if the interest
rate is 6% per annum.