1.
3 resistors of 4 ohms are placed in series - what is their combined (equivalent) resistance?
Correct Answer
D. 12 ohms
Explanation
When resistors are connected in series, their resistances add up to give the total resistance. In this case, since there are three resistors of 4 ohms each, the combined resistance is 4 + 4 + 4 = 12 ohms.
2.
2 resistors each of 4 ohms are in parallel - what is their combined (equivalent) resistance?
Correct Answer
B. 2 ohms
Explanation
When resistors are connected in parallel, the total resistance is calculated using the formula 1/RT = 1/R1 + 1/R2, where RT is the total resistance and R1 and R2 are the resistances of the individual resistors. In this case, since both resistors have a resistance of 4 ohms, substituting the values into the formula gives 1/RT = 1/4 + 1/4 = 1/2. Solving for RT gives a total resistance of 2 ohms.
3.
3 resistors of resistances 4 ohms, 4 ohms and 2 ohms are in parallel with each other. What is their combined resistance?
Correct Answer
A. 1 ohm
Explanation
When resistors are connected in parallel, the total resistance is calculated using the formula: 1/RTotal = 1/R1 + 1/R2 + 1/R3 + ...
In this case, the resistances of the three resistors are 4 ohms, 4 ohms, and 2 ohms. Plugging these values into the formula, we get: 1/RTotal = 1/4 + 1/4 + 1/2 = 2/4 + 2/4 + 4/4 = 8/4 = 2
Taking the reciprocal of both sides, we find that RTotal = 1/2 = 0.5 ohms. Therefore, the combined resistance of the three resistors is 0.5 ohms, which is not one of the given answer choices. Since none of the answer choices match the correct value, the given answer of 1 ohm is incorrect.
4.
What can you say about an ideal Voltmeter?
Correct Answer
B. Resistance is infinite
Explanation
An ideal voltmeter is one that has infinite resistance. This means that when connected in parallel to a circuit, it draws no current from the circuit and does not affect the voltage being measured. It provides an accurate measurement of the potential difference (PD) across a component or between two points in a circuit without altering the circuit's behavior. An infinite resistance ensures that the voltmeter does not create a parallel path for current to flow, allowing it to measure the voltage without disturbing the circuit.
5.
What can you say about an ideal Ammeter?
Correct Answer
A. Resistance is zero
Explanation
An ideal ammeter is a device used to measure electric current in a circuit. It is considered ideal when its resistance is zero. This means that it does not introduce any resistance into the circuit, allowing for accurate measurement of the current flowing through it. A zero resistance ammeter ensures that the current being measured is not affected or altered by the presence of the ammeter itself.
6.
Which sentence below best describes the behaviour of a Thermistor
Correct Answer
F. High resistance when it is cool.
Explanation
A thermistor is a type of resistor whose resistance changes with temperature. It is designed to have a high resistance when it is cool and a low resistance when it is hot. This behavior allows thermistors to be used in temperature sensing applications, where they can measure and respond to changes in temperature.
7.
Which sentence below best describes the behaviour of a LDR
Correct Answer
B. Low resistance with high light intensity
Explanation
LDR stands for Light Dependent Resistor, which means it is a resistor that changes its resistance based on the intensity of light that falls on it. The correct answer states that LDR has low resistance when the light intensity is high. This means that when there is a lot of light, the LDR allows more current to flow through it, resulting in a lower resistance. Conversely, when the light intensity is low, the LDR has high resistance, limiting the current flow.
8.
Which sentence below best describes the behaviour of a Strain gauge?
Correct Answer
C. High resistance when it is stretched
Explanation
A strain gauge is a device that measures the strain or deformation of an object. When the strain gauge is stretched, its resistance increases. This is because the stretching causes the metal wire in the strain gauge to elongate, resulting in an increased resistance to the flow of electric current. Therefore, the statement "High resistance when it is stretched" best describes the behavior of a strain gauge.
9.
Are there any areas of this section on resistors in series and parallel, ammeters and voltmeters and potential dividers which are confusing?