A resistor develops 400J of thermal energy in 10 s when a current of 2A is pased through it. (a) Find its resistance . (b) If the current is increased to 4 A, what will be the energy developed in 10 s.

Explanation

(a) using `U=i^(2)Rt,`
`400J=(2 A)^(2) R(10 s)`
or, `R=10(Omega).`
(b) The thermal energy devoloped, when the current is 4 A, is
`U=i^(2)Rt`
`=(4A)^(2)xx(10(Omega))xx(10s)=1600J.`