Fixed Resistor
Question: Draw the I-V characteristic graph for a fixed resistor and explain why the graph is a straight line.
Answer: The I-V characteristic graph for a fixed resistor is a straight line that passes through the origin. This is because the resistance (R) is constant, and according to Ohm's Law (V = IR), the current (I) is directly proportional to the voltage (V). Hence, the graph is a straight line with a slope equal to the resistance.
Thermistor
Question: Describe how the resistance of a thermistor changes with temperature and draw the corresponding I-V characteristic graph.
Answer: The resistance of a thermistor decreases as the temperature increases. This is because thermistors are made of semiconductor materials whose resistance decreases with rising temperature. The I-V characteristic graph of a thermistor shows that as the temperature increases, the current for a given voltage increases, indicating a decrease in resistance.
Diode
Question: Sketch the I-V characteristic graph for a diode and explain the behavior in both forward and reverse bias.
Answer: The I-V characteristic graph for a diode shows that in forward bias (positive voltage), the current increases exponentially after the threshold voltage is reached. In reverse bias (negative voltage), the current is very small (almost zero) until the breakdown voltage is reached, where it increases rapidly. This behavior is due to the diode allowing current to flow easily in one direction (forward) while blocking it in the opposite direction (reverse).
LDR
Question: Explain how the resistance of an LDR changes with light intensity and draw the I-V characteristic graph for an LDR.
Answer: The resistance of a Light Dependent Resistor (LDR) decreases as the light intensity increases. This is because more light photons provide more energy to the semiconductor material, creating more charge carriers and thus reducing resistance. The I-V characteristic graph of an LDR shows that for higher light intensity, the current for a given voltage increases, indicating lower resistance.
Filament Lamp
Question: Why does the I-V characteristic graph of a filament lamp curve and flatten at higher voltages?
Answer: The I-V characteristic graph of a filament lamp curves and flattens at higher voltages because as the current increases, the temperature of the filament increases. This increased temperature causes the resistance of the filament to increase, which in turn reduces the rate of increase of current, resulting in a curve that flattens at higher voltages.
Static Electricity
Question: Explain how static electricity can be generated by friction.
Answer: Static electricity can be generated by friction when two materials are rubbed together, causing electrons to be transferred from one material to the other. This transfer of electrons creates an imbalance of charges, leading to one object being positively charged and the other negatively charged.
Question: Describe an experiment to demonstrate the presence of static electricity.
Answer: One simple experiment to demonstrate static electricity is to rub a balloon on your hair and then bring it close to small pieces of paper. The static charge on the balloon will attract the paper pieces, demonstrating the presence of static electricity.
Question: How can you safely discharge a charged object?
Answer: You can safely discharge a charged object by touching it with a conductor connected to the ground (earth). This allows the excess electrons to flow away from the object, neutralizing its charge.