A resistor with resistance R is connected to a battery that has emf 13.0 V and internal resistance r = 0.350 Ω . For what two values of R will the power dissipated in the resistor be 81.0 W ?

The two values of R when the power dissipated is 81 W are 1.74 ohms or -0.35 ohms.

The given parameters;

The current flowing in the circuit is calculated as follows;

E = IR + Ir

E = I(R + r)

-----(1)

The power dissipated in the circuit is calculated as follows;

P = I²(R + r)

solve (1) and (2) together;

Thus, the two values of R when the power dissipated is 81 W are 1.74 ohms or -0.35 ohms.

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R = 1,746 Ω

Explanation:

The power dissipated in the circuit is

   P = V I = V² / R

Let's find the current

   R = V² / P

Let's calculate

  R = 13²/81

   R = 2,096 Ω

This is total resistance

  R_total = R + r

   R = R_total - r

   R = 2,096 -0,350

   R = 1,746 Ω

neither accurate nor precise.

i had this question and the answer was 3.15 miles.

martina travels from school to her mom's office. from there, she walks to school. after school, she walks to the library and then to a friends house before finally ending back at home. find martina's total distance traveled.

a) 0 miles  

b) 0.4 miles  

c) 1 mile  

d) 3.15 miles