18 Questions
In an ohmic conductor, how is the current related to the potential difference?
Current is directly proportional to the potential difference
What type of biasing occurs in a semiconductor diode when the current flows in the direction of the arrowhead symbol?
Forward bias
How does a semiconductor diode behave when it is in reverse bias?
Shows a zero reading of current or potential difference
What type of graph is observed for an LED in terms of I-V characteristics?
Sharp increase in potential difference further away from the origin
In a circuit, what does a diode allow to flow only in a specific direction?
Current
Which of the following correctly describes the behavior of an ohmic conductor at a constant temperature?
The current is directly proportional to the potential difference
What happens to the resistance of a metallic conductor when the temperature increases?
It increases
In a metallic conductor under the influence of Ohm's law, how does an increase in temperature affect the resistivity?
It increases
What is the relationship between resistivity and resistance in a metallic conductor?
Directly proportional
How does a decrease in temperature affect the resistivity of a semiconductor?
It decreases
Which type of material shows an increase in resistivity with an increase in temperature?
Metallic conductor
What happens to the resistivity of a material as its resistance increases?
Resistivity increases
What is the expected shape of the I-V graph for an ohmic conductor?
Straight line
What is the relationship between voltage (V), current (I), and resistance (R) in Ohm's Law?
$V = IR$
What type of conductor would show a curve on the I-V graph?
Filament lamp
What is the effect of temperature on the resistivity of metals?
Increases resistivity
Which component would typically exhibit semiconductor behavior?
Diode
How does the resistivity of an insulator compare to that of a conductor?
Insulator resistivity is higher than conductor resistivity
Study Notes
Conductor Types and Characteristics
- Ohmic Conductor (e.g., Resistor):
- I-V graph is a straight line through the origin
- Current is directly proportional to potential difference
- Semiconductor Diode:
- I-V graph has a sharp increase in potential difference and current on the right side (forward bias)
- No current or potential difference on the left side (reverse bias)
- LED:
- I-V graph identical to diode, except the sharp increase is further away from the origin
- The frequency of the light increases as the sharp increase moves away from the origin
Resistance and Resistivity
- Resistivity of a material depends on its temperature
- If the cross-sectional area of a wire is circular, it is proportional to the diameter squared
- If the diameter doubles, the area quadruples, causing the resistance to drop by a quarter
Variation of Resistivity with Temperature
- Metals:
- Resistivity increases with increasing temperature due to increased vibration of atoms, impeding electron flow
- An increase in temperature causes an increase in resistance and resistivity
- A decrease in temperature causes a decrease in resistance and resistivity
I-V Graph Analysis
- A straight-line I-V graph indicates an ohmic conductor (obeys Ohm's Law: V = IR)
- A curved I-V graph indicates a non-ohmic conductor
Test your knowledge on the I-V characteristics of components such as ohmic conductors, semiconductor diodes, filament lamps, LEDs, and thermistors. Understand the differences in the graphs for each component at constant temperature and how they behave under varying voltages.
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