Redraw the circuit of 9.39, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the `12Omega` resistor. What would be the readings in the ammeter and the voltmeter ?

Explanation

The circuit diagram of above with an ammeter A and a voltmeter Vacross `12Omega` resistor is shown in figure

Calculation of current flowing in the circuit :
Equivalent resistance of the circuit,
`R_s = 5Omega + 8 Omega + 12 Omega = 25 Omega`
In a series combination, the current flowing through each resistor is the same and equal to the total current flowing through the circuit.
`:.` Current through the resistors,
`I + V/R`
`= 6/25`
`= 0.24 A`
Since the current in the circuit and the current through each resistor is the same, the ammeter will show a reading of 0.24 A.
Calculation of potential difference across 122 resistor :
As total current 0.24 A flows in the circuit, the same current 0.24 A would also flow through the 122 resistor which is connected in series.
`:.` The potential difference across the 12 12 resistor,
`V = IR`
` = 0.24 xx 12 = 2.88 V`
Thus, the p.d. across `12 Omega` resistor is 2.88 volt.
So, the voltmeter will show a reading of 2.88 V.