Question

device for heating a cup of water in a car connects to the car's battery, which has an emf E = 10.0 V and an internal resistance rint = 0.07 Ω . The heating element that is immersed in the cup of water is a resistive coil with resistance R.

Answer 1

R = 0.93 ohms

Step-by-step explanation:

Let's start by calculating the resistance of the coil,

V = I ( R + r )

Make R the subject of the above equation.

Hence,

V = IR + Ir

V - Ir = IR

( V - Ir )/I = R

Given that V = 10V

r = 0.07ohms

I = 10A ( this is an assumption )

( 10 - 10×0.07 ) ÷ 10

R = 0.93 ohms

Note: r is the internal resistance, R is the resistance, I is the current and the emf is represented as V. Since current was supposed to be included in the question but it was not, hence it was assumed to be 10A . Meaning whatsoever value is given for current will be substituted into the equation. Thanks