How is a voltmeter connected in the circuit to measure the potential difference between two points explain with the help of a diagram Class 10?

An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?

Given,
Resistance of electric lamp, R1 = 100 Ω
Resistance of toaster, R2 = 50 Ω
Resistance of water filter, R3 = 500 Ω 

Equivalent resistance, Rp of the three appliances connected in parallel is given by,

            1Rp = 1R1+1R2+1R3

                  = 1100+150+1500= 16500

            Rp = 50016Ω      = 31.25 Ω 

Resistance of electric iron will be equivalent resistance of the three appliances connected in parallel = 31.25 Ω Applied voltage, V = 220 V 

Current through the appliance, I = VR = 220 V31.25Ω =7.04 A.