Resistance in Sensory Resistor

The resistance of one device R1 is designed to change with temperature; the resistance of another device R2 is designed to change with illumination.

What are the names of these devices?

• R1 = thermistor

  R2 = light-dependent resistor

• R1 = thermistor

  R2 = potential divider

• R1 = semiconductor diode

  R2 = light-dependent resistor

• R1 = semiconductor diode

  R2 = potential divider

A light-dependent resistor (LDR) is connected in series with a resistor R and a battery. The resistance of the LDR is equal to the resistance of R when no light falls on the LDR. When the light intensity falling on the LDR increases, which statement is correct?

• the current in R decreases

• the current through the LDR decreases

• the p.d. Across R decreases

• the p.d across the LDR decreases

Which graph best represents the way in which the current I through a thermistor depends upon the potential difference V across it?

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A circuit is set up with an LDR and a fixed resistor as shown.

The voltmeter reads 4V.

The light intensity is increased.

What is a possible voltmeter reading?

• 3V

• 4V

• 6V

• 8V

In the circuit below, the reading VT on the voltmeter changes from high to low as the temperature of the thermistor changes. The reading VL on the voltmeter changes from high to low as the level of light on the light-dependent resistor (LDR) changes. 

The readings VT and VL are both high. 

What are the conditions of temperature and light level?

• Temperature: low

  Light level: low

• Temperature: low

  Light level: high

• Temperature: high

  Light level: low

• Temperature: high

  Light level: high

The resistance of a thermistor depends on its temperature, and the resistance of a light-dependent resistor (LDR) depends on the illumination.

Under which conditions will the resistance of both a thermistor and an LDR be highest?

• thermistor: highest temperature

  LDR: highest illumination

• thermistor: highest temperature

  LDR: lowest illumination

• thermistor: lowest temperature

  LDR: highest illumination

• thermistor: lowest temperature

  LDR: lowest illumination

A thermistor and another component are connected to a constant voltage supply. A voltmeter is connected across one of the components. The temperature of the thermistor is then reduced, but no other changes are made.

In which circuit will the voltmeter reading increase?

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