Electronics Engineering (ELEX) Board Practice Exam

To determine the resistance of a copper wire at a different temperature, you can use the temperature coefficient of resistance formula. For copper, the temperature coefficient is approximately 0.00393 per degree Celsius.

The resistance of a conductor at a temperature can be calculated with the equation:

\[ R_t = R_0 (1 + \alpha (T_t - T_0)) \]

Where:

- \( R_t \) is the resistance at temperature \( T_t \).

- \( R_0 \) is the resistance at the initial temperature \( T_0 \).

- \( \alpha \) is the temperature coefficient of resistance.

- \( T_t \) is the final temperature.

- \( T_0 \) is the initial temperature.

Given:

- \( R_0 = 200 \, \Omega \)

- \( T_0 = 20°C \)

- \( T_t = 90°C \)

Now, substituting the values into the equation:

1. Calculate the temperature difference:

\[ T_t - T_0 = 90°C - 20°C = 70°C \]

2. Using the temperature coefficient for copper:

\[ \alpha = 0.00393 /