Component Characteristics

Question 1

What does current-potential difference graph for a resistor show?

Answer 1

The graph shows a straight line through the point of orgin.

Question 2

What is the relationship between the potential difference and the current for a resistor?

Answer 2

The current is directly proportional to the potential difference. In other words the resistance is constant.

Question 3

What is Ohm’s law?

Answer 3

The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.

Question 4

What is an ohmic conductor?

Answer 4

A conductor which shows it’s resistance does not depend on the current.

Question 5

What does the gradient of a line in a graph depend on?

Answer 5

The gradient of the line depends on the resistance of the resistor. The greater the resistance of the the resistor.

Question 6

What does the graph for potential difference and current look like for a filament lamp?

Answer 6

1. The line curves away from the y-axis, so the current is not directly proportional to the potential difference. As this is a non-linear graph the filament lamp is a non-ohmic conductor.

Question 7

What is the relationship between the resistance and temperature of the lamp?

Answer 7

The resistance of a filament lamp increases as the filament temperature increases. The atoms in the filament vibrate more as the temperature increases, so they resist the passage of the electrons through the filament more. The resistance of any metal increases as its temperature increases.

Question 8

What does the current-potential difference graph look like for a diode?

Answer 8

1. In the forward direction, the line curves towards the y-axis, so the current is not directly proportional to the potential difference. The resistance changes as the current changes. A diode is a non-ohmic conductor.
2. In the reverse direction, the current is virtually zero, so the diode’s resistance in the reverse direction is a lot higher than it’s resistance is in the forward direction.

Question 9

What is an LED?

Answer 9

A light emitting diode is a diode that emits light when a current passes through it. LED’s are currently being used in home lighting, backlights in LCD screens and as indicator lights on many electronic devices such as battery charges and alarm circuits.