5). A conductor of radius r, length & and resistivity p has resistance R. It is melted down and formed into a new conductor, also cylindrical, with one fourth the length of the original conductor. The resistance of the new conductor is a. 1 R 161 b. 1 R C. R d. 4R e. 16R

Check Your Understanding Handheld calculators often use small solar cells to supply the energy required to complete the calculations needed to complete your next physics exam. The current needed to run your calculator can be as small as 0.30 mA. How long would it take for 1.00 C of charge to flow from the solar cells? Can solar cells be used, instead of batteries, to stall traditional internal combustion engines presently used in most cars and trucks?

(Indicates a review question, which means it requires only a basic understanding of the material to answer. Questions without this designation typically require integrating or extending the concepts presented thus far.) . Six resistors, all having the same temperatures and compositions, are each attached to a battery with voltage V to form a simple circuit. The resistors have different lengths, l, but the same diameters. Rank the circuits according to the current that flows through the resistor from smallest to greatest. If two (or more) circuits have the same current flowing, give them the same ranking. Explain the rationale you used to establish your rankings. Circuit 1: l = 2 cm; V = 3 V Circuit 2: l = 2 cm; V = 6 V Circuit 3: l = 1 cm; V = 3 V Circuit 4: l = 1 cm; V = 6 V Circuit 5: l = 3cm; V = 2 V Circuit 6: l = 3cm; V = 6 V

Check Your Understanding A strain gauge is an electrical device to measure strain, as shown below. It consists of a flexible, insulating backing that supports a conduction foil pattern. The resistance of the foil changes as the backing is stretched. How does the strain gauge resistance change? Is the strain gauge affected by temperature changes?

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

What is die basic operation of an ohmmeter as it measures a resistor?

A 12.0-V emf automobile battery has a terminal voltage of 16.0 V when being charged by a current of 10.0 A. (a) What is the battery’s internal resistance? (b) What power is dissipated inside the battery? (c) At what rate (in °C/min ) will its temperature increase if its mass is 20.0 kg and it has a specific heat of 0.300 kcal/kg • °C, assuming no heat escapes?

In Figure 21.41. does the graph indicate the time constant is shorter for discharging than for charging? Would you expect ionized gas to have low resistance? How would you adjust R to get a longer time between flashes? Would adjusting R affect the discharge time?

(Indicates a review question, which means it requires only a basic understanding of the material to answer. Questions without this designation typically require integrating or extending the concepts presented thus far.) . A solid metal cylinder has a certain resistance. It is then heated and carefully stretched to form a longer, thinner cylinder. After it cools, will its resistance be the same as, greater than, or less than what it was before? Explain our choice.

The quantity of charge q (in coulombs) that has passed through a surface of area 2.00 cm2 varies with time according to the equation q = 4t3 + 5t + 6, where t is in seconds. (a) What is the instantaneous current through the surface at t = 1.00 s? (b) What is the value of the current density?