The figure shows a circuit.
When the circuit is switched on, the ammeter reads 0.5A.

Calculate the value of the unknown resistor R.

Explanation

`I=(V )/(R ) ` here ` R .=3 +R`
` implies 0.5 = ( 6.0 )/(3 +R)`
` implies 3 + R = ( 6.0 )/(0.5)`
` implies R=(60 )/(5 ) 3=12 - 3 9 Omega `