There are a variety of sensors which work on the basis of changing resistance du

Question

There are a variety of sensors which work on the basis of changing resistance due to an external influence. For example, force-sensitive resistors (FSR) will change their resistance when a force is a exerted (when you squeeze them).

Computers are good at reading out voltages, so these devices are often combined ith a fixed-value resistor to create a voltage divider circuit. Consider the circuit shown below where the fixed resistor, R, has a resistance of 20.0 k? and the FSR has a resistance of 80.0 k? when there is no force acting on the FSR. A voltage V=5.00 V is being applied to the two series resistors.

What is the current flowing through the FSR when there is no force being applied to the FSR?
5.00×10-5 A

What is the current flowing through the fixed resistor when there is no force being applied to the FSR?
5.00×10-5 A

Consider the negative terminal of the voltage source to be at a potential of zero Volts. What is the electric potential (voltage) at the location A between the two resistors?
1.00 V

Suppose that if a force of 1.20 N is applied to the FSR, its resistance decreases to 4.00 k?. What would be the new current through the fixed resistor, R?
0.000208 A

What would be the electric potential at Location A between the two resistors with the applied force of 1.20 N?

Explanation / Answer

a)

curret through FSR

I= 5/(20k+80k) = 5*10-5 Ampere

b) since both FSR and fixed resistor are in series curent will be same

hence current throuh R is also

I= 5/(20k+80k) = 5*10-5 Ampere

c) voltage at location A is

V -0 =   5*10-5 * 20*103 = 1 volt

d) I = 5/(20k+76k) = 0.000208 A

e) potential at A

V-0= 0.000208* 20*103 = 4.166 volt

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