Question

The following apparatus is available in a laboratory :
Battery : adjustable from 0 to `4.5 V`
Resistors : `3 Omega` and `6 Omega`
Ammeters : `A_1` of range 0 to 3 A , least count `0.1 A`
`A_2` of range 0 to 1 A , least count `0.05 A`
Voltmeters : `V_1` of range 0 to 10 V , least count `0.5 V`
`V_2` of range 0 to 5 V , least count `0.1 V`
Which is the best combination of votmeter and ammeter for finding the equivalent resistance of the resistors in series ?

Answer 1

Equivalent resistance `= 3 Omega + 6 Omega = 9 Omega`
Maximum current to be measured `= (4.5 V)/(9 Omega) = 0.5 A`
Maximum voltage to be measured `(9 Omega)(0.5 A) = 4.5 V`
Ammeter `A_2` and voltmeter `(V_2)` fulfil these requirements of measuring current and voltage. Apart from this, these two instruments have maximum accuracy due to their smaller least counts `(0.05 A and 0.1 V "respectively")`.