Question

A resistor rated at 250 k Ω is connected across two D cell batteries (each 1.50 V) in series, with a total voltage of 3.00 V. The manufacturer advertises that their resistors are within 5% of the rated value. What are the possible minimum current and maximum current through the resistor?

Answer 1

Given Information:  

Resistance = R = 250 Ω

Voltage = V = 3 V

Tolerance =   ±5%

Required Information:  

Maximum current = Imax = ?

Minimum current = Imin = ?

Answer:  

Imax = 12.6 uA

Imin = 11.4 uA

Explanation:  

As we know from Ohm's law

I = V/R

The current will be maximum when R is minimum and the current will be minimum when R is maximum

Rmax = 250,000 + 0.05*250,000

Rmax = 250,000 + 12500

Rmax = 262500 Ω

Rmin = 250,000 - 0.05*250,000

Rmin = 250,000 - 12500

Rmin = 237500 Ω

Imax = V/Rmin

Imax = 3/237500

Imax = 12.6 uA

Imin = V/Rmax

Imin = 3/262500

Imin = 11.4 uA