AP Physics 2 : Resistors and Resistance
Study concepts, example questions & explanations for AP Physics 2
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Example Questions
Example Question #321 : Electricity And Magnetism
Which of the following changes to a circuit will increase its overall resistance?
Decreasing the overall length of the circuit's conducting material
Adding a new resistor in parallel with another resistor in the circuit
Increasing the cross-sectional area of the wire that is used to carry the current
Decreasing the resistivity of the wire carrying the current
Adding a new resistor in series with another resistor in the circuit
Adding a new resistor in series with another resistor in the circuit
In this question, we're asked to identify an answer choice that will increase the overall resistance of a circuit.
All conducting materials have an intrinsic resistance. This kind of resistance, called resistivity, is dependent on the type of material used to conduct the current. In addition to this, resistance is also dependent on the length of the conducting material as well as the cross-sectional area. A shorter length will lead to a smaller amount of resistance. Likewise, a larger cross-sectional area will result in decreased resistance.
Furthermore, it's important to recall that resistors add in series but add inversely in parallel. The reason for this is because resistors connected in series must all have the same current flowing through them. Because the sum total of the voltage drop of each of them must equal the overall voltage supplied by the external voltage source, the overall current (which will flow through each of them) is decreased. For a constant voltage, a decreased current means that the circuit as a whole must have a greater resistance.
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