Calculate the resistances of the following combinations:

$100 \mathrm{\Omega }$ and $200 \mathrm{\Omega }$ in series and this in parallel with $200 \mathrm{\Omega }.$

Calculate the current drawn from a $12 \mathrm{V}$ battery of negligible internal resistance connected to the ends of the following: 

(a). $500 \mathrm{\Omega }$ resistor

Calculate the current drawn from a $12 \mathrm{V}$ battery of negligible internal resistance connected to the ends of the following: 

(b). $500 \mathrm{\Omega }$ and $1000 \mathrm{\Omega }$ resistors in series 

Calculate the current drawn from a $12 \mathrm{V}$ battery of negligible internal resistance connected to the ends of the following: 

$500 \mathrm{\Omega }$and $1000 \mathrm{\Omega }$ resistors in parallel.

Three resistors of resistances $20 \mathrm{\Omega }, 30 \mathrm{\Omega }$ and $60 \mathrm{\Omega }$ are connected together in parallel. Select which of the following gives their combined resistance: $110 \mathrm{\Omega }, 50\mathrm{\Omega }, 20\mathrm{\Omega },10\mathrm{\Omega }$ 
(No need to do the calculation)

In the circuit in Figure the battery of e.m.f.$10 \mathrm{V}$ has negligible internal resistance. Calculate the current in the $20 \mathrm{\Omega }$ resistor shown in the circuit.

Determine the current drawn from the battery in Figure.