9.3 Resistivity and resistance  (Page 6/10)

The IR drop across a resistor means that there is a change in potential or voltage across the resistor. Is there any change in current as it passes through a resistor? Explain.

Do impurities in semiconducting materials listed in [link] supply free charges? ( Hint : Examine the range of resistivity for each and determine whether the pure semiconductor has the higher or lower conductivity.)

Does the resistance of an object depend on the path current takes through it? Consider, for example, a rectangular bar—is its resistance the same along its length as across its width?

If aluminum and copper wires of the same length have the same resistance, which has the larger diameter? Why?

What current flows through the bulb of a 3.00-V flashlight when its hot resistance is $3.60\text{Ω}$ ?

Calculate the effective resistance of a pocket calculator that has a 1.35-V battery and through which 0.200 mA flows.

How many volts are supplied to operate an indicator light on a DVD player that has a resistance of $140\text{Ω}$ , given that 25.0 mA passes through it?

What is the resistance of a 20.0-m-long piece of 12-gauge copper wire having a 2.053-mm diameter?

The diameter of 0-gauge copper wire is 8.252 mm. Find the resistance of a 1.00-km length of such wire used for power transmission.

If the 0.100-mm-diameter tungsten filament in a light bulb is to have a resistance of $0.200\text{Ω}$ at $20.0\text{°}\text{C}$ , how long should it be?

A lead rod has a length of 30.00 cm and a resistance of $5.00\mu \text{Ω}$ . What is the radius of the rod?

Find the ratio of the diameter of aluminum to copper wire, if they have the same resistance per unit length (as they might in household wiring).

What current flows through a 2.54-cm-diameter rod of pure silicon that is 20.0 cm long, when $1.00\times {10}^3\text{V}$ is applied to it? (Such a rod may be used to make nuclear-particle detectors, for example.)

(a) To what temperature must you raise a copper wire, originally at $20.0\text{°}\text{C}$ , to double its resistance, neglecting any changes in dimensions? (b) Does this happen in household wiring under ordinary circumstances?

A resistor made of nichrome wire is used in an application where its resistance cannot change more than 1.00% from its value at $20.0\text{°}\text{C}$ . Over what temperature range can it be used?

Of what material is a resistor made if its resistance is 40.0% greater at $100.0\text{°}\text{C}$ than at $20.0\text{°}\text{C}$ ?

An electronic device designed to operate at any temperature in the range from $\mathrm{-10.0}\text{°}\text{C}$ to $55.0\text{°}\text{C}$ contains pure carbon resistors. By what factor does their resistance increase over this range?

(a) Of what material is a wire made, if it is 25.0 m long with a diameter of 0.100 mm and has a resistance of $77.7\text{Ω}$ at $20.0\text{°}\text{C}$ ? (b) What is its resistance at $150.0\text{°}\text{C?}$

Assuming a constant temperature coefficient of resistivity, what is the maximum percent decrease in the resistance of a constantan wire starting at $20.0\text{°}\text{C}$ ?

A copper wire has a resistance of $0.500\text{Ω}$ at $20.0\text{°}\text{C},$ and an iron wire has a resistance of $0.525\text{Ω}$ at the same temperature. At what temperature are their resistances equal?