Question

The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.

Answer 1

(i) when k is open 

Req = 5Ω + 0.5 Ω = 5.5Ω 

(ii) `i = v/(R_(eq))|_("case k open")`

`=(3.3v)/(5.5 Ω ) = 3/5 =0.6 A`

(iii) when k is closed,

`R_(eq) =(R_1R_2)/(R_1 + R_2) = (5xx5)/(5+5) = 2.5 Ω`

`R_(Total) = 2.5 Ω + 0.5 Ω = 3.0 Ω`

(iv) `i =v/(R_T) = 3.3/3.0 = 1.1A`