A problem from my book-10!

An Ammeter and a voltmeter is shown in figure-1 . A naughty boy came and interchange the markings of ammeter and voltmeter together as shown in figure-2

(now if the actual potential drop across voltmeter is 6 V it will show 4V)

. Now the changed ammeter and voltmeter is connected in a R-C circuit as shown in figure-3 .

The resistance is of 0.25 ohm and capacitor is of 4 micro farad.. Find the time in which both the ammeter and voltmeter show same readings.( E<1V)

The answer is of form t= (10^a ) ln(b) s. Find a x b.

Note:-

• ammeter and voltmeter are not interchanged only there markings are interchanged.

• it is obvious that if we are using voltmeter readings is in volts and if we are using ammeter reading is in amperes

• Assume voltmeter ,ammeter and battery ideal