State Ohm's Law - Leaving Cert Physics - Question 8 - 2005

The metal conductor obeys Ohm's law. The graph of current ( I) varying with potential difference ( V) shows a straight line, indicating a linear relationship between the two variables. This linear relationship signifies that the resistance remains constant, which is a fundamental characteristic of materials that obey Ohm’s law.

To find the total resistance ( R_t) of the circuit, we simply add the resistances of the components in series:

$R_t = R_1 + R_2$

where R_1 = 100 Ω and R_2 = 500 Ω:

$R_t = 100 + 500 = 600 Ω$

Using Ohm's Law, we can find the current ( I) flowing through the circuit:

$I = \frac{V}{R_t}$

Since the total voltage ( V) is 6 V and the total resistance ( R_t) is 600 Ω:

$I = \frac{6}{600} = 0.01 A$

To find the potential difference ( V_1) across the 100 Ω resistor, we again use Ohm's Law:

$V_1 = I imes R_1$

Where I = 0.01 A and R_1 = 100 Ω:

$V_1 = 0.01 imes 100 = 1 V$

As the thermistor is heated, its resistance decreases. This is because thermistors are temperature-sensitive resistors, and generally, resistance decreases as temperature increases.

As the resistance of the thermistor decreases, the total resistance in the circuit decreases, resulting in an increase in the current. Therefore, the potential difference across the 100 Ω resistor will also increase, as it is directly proportional to the current flowing through it.

Thermistors are commonly used as temperature sensors. They can be utilized in appliances like digital thermometers, and HVAC systems for temperature control and monitoring.