A 10 Ω resistor is required for use in a circuit where the potential difference across it will be 4 V. What should its power rating be? Resistors of resistances 20 Ω, 30 Ω and 50 Ω are connected in...

A 10 Ω resistor is required for use in a circuit where the potential difference across it will be 4 V. What should its power rating be?

Resistors of resistances 20 Ω, 30 Ω and 50 Ω are connected in series across a DC supply of 20 V. What is the current in the circuit and the potential difference across each resistor?