Concept explainers
The ranking of the given actions in terms of the change in current from greatest increase to the greatest decrease.
Answer to Problem 3OQ
The ranking of current in decreasing order is given by
Explanation of Solution
Write the expression for the Ohm’s Law.
Here,
Write the expression for the power in terms of voltage.
Here,
Write the expression for the resistance.
Here,
Write the expression for the current in terms of potential difference.
Here,
Write the expression for the resistance of the wire in terms of temperature.
Here,
Case (a):
Substitute
Substitute
Substitute
Therefore, the current is
Case (b):
Rearrange equation (II) to find voltage.
Write the expression for the ratio of the voltages at power
Substitute
Substitute
Therefore, the value of current for triple power is
Case (c):
Substitute equation (III) in equation (I) to find
Substitute
Write the expression for voltage
Write the expression for the ratio of
Substitute
Therefore, the current is
Case (d):
Substitute equation (III) in equation (I) to find
Write the expression for voltage
Write the expression for the ratio of voltage
Substitute
Therefore, then current is
Case (e):
From equation (V), it is clear that resistance is proportional to temperature
Hence, when temperature is doubled, the resistance is also doubled.
The ratio of voltages from equation (I) is given by:
Substitute
Therefore, the current is
Conclusion:
Therefore, the ranking of current in the decreasing order is given by
Want to see more full solutions like this?
Chapter 27 Solutions
Physics: for Science.. With Modern. -Update (Looseleaf)
- Taking R = 1.00 k and = 250 V in Figure P21.49, determine the direction and magnitude of the current in the horizontal wire between a and e. Figure P21.49arrow_forwardA potential difference of 1.00 V is maintained across a 10.0- resistor for a period of 20.0 s. What total charge passes by a point in one of the wires connected to the resistor in this time interval? (a) 200 C (b) 20.0 C (c) 2.00 C (d) 0.005 00 C (e) 0.050 0 Carrow_forwardA 0.900-V potential difference is maintained across a 1.50-m length of tungsten wire that has a cross-sectional area of 0.600 mm2. What is the current in the wire?arrow_forward
- The earth’s surface has a negative surface charge density of 10-9 C m-2. The potential difference of 400 kV between the top of the atmosphere and the surface results (due to the low conductivity of the lower atmosphere) in a current of only 1800 A over the entire globe. If there were no mechanism of sustaining atmospheric electric field, how much time (roughly) would be required to neutralise the earth’s surface? (This never happens in practice because there is a mechanism to replenish electric charges, namely the continual thunderstorms and lightning in different parts of the globe). (Radius of earth = 6.37 × 106 m.)arrow_forwardTaking R = 1.50 kΩ and ε = 150 V in the figure shown below, determine the magnitude and direction of the current in the horizontal wire between a and e. 17.5 mA, from e to a19.9 mA, from a to e 18.0 mA, from e to a18.9 mA, from a to e18.0 mA, from a to e19.9 mA, from e to aarrow_forwardYou want to design a heating element that dissipates 5 kW by maintaining a 75.0 V potential difference across the ends of Nichrome wire with a cross section of 2.5 × 10−6 m2 . How long should the wire be?arrow_forward
- A Nichrome heater dissipates 500 W when the appliedpotential difference is 110 V and the wire temperature is 800 C.What would be the dissipation rate if the wire temperature wereheld at 200 C by immersing the wire in a bath of cooling oil? Theapplied potential difference remains the same, and a for Nichromeat 800 C is 4.0 * 10-4 K-1.arrow_forwardThe current in a certain wire at 20.0°C is 2.40 A when thepotential difference between the ends of the wire is 1.50 V. Ifthe wire is heated to 80.0°C and the potential differenceremains the same, the current decreases to 2.00 A. (a) What isthe resistance of the wire at 20.0°C? At 80.0°C? (b) What is thetemperature coefficient of resistivity for the material of whichthis wire is made?arrow_forwardQ2. To determine the galvanometer's internal resistor R. and its maximum electric current Is, corresponding to a maximum deviation of its needle, we mount it in series with a rheostat, as shown in the adjacent figure. R a b son Reosta Galvanometre When the needle makes a maximum deviation Vab = V1 = 5 V and Rr= R1 = 80 k 2. When the needle makes 1/2 maximum deviation Vab = V2 = 2 V and Rp = R2 = 60 ko. When the needle makes 44 maximum deviation Vab = V3 = 2 V and Rr = R3 . V a) Write the relationship between V1, R1, Rc and le. b) Write the relationship between V2, R2, Re and Ic. c) Write the relationship between V3, R3, Re and Ic. d) Determine the values of Re and Ic. e) Determine the value of Rs. Answer:arrow_forward
- If connected to a 3 V potential difference, a certain resistor dissipates 0.5 W. How much energy would the resistor dissipate if it is connected to a 1 V potential difference? A. 0.056 W. B. 0.167 W. C. 0.5 W. D. 1.5 W. E. Cannot be determined.arrow_forwardA spool of tungsten wire 200 m long and with a diameter of 0.360 mm is at 20.0°C. For tungsten, the resistivity is 5.60 ✕ 10−8 Ω · m and the temperature coefficient of resistivity is 4.50 ✕ 10−3 (°C)−1. (a) What is the magnitude of the electric field (in V/m) in the wire if it carries a current of 0.450 A? V/m (b) What is the electric power (in W) delivered to the spool while it carries a current of 0.450 A? W (c) What is the power (in W) delivered to the spool if the potential difference across the wire is held constant and the temperature is increased to 310°C? Warrow_forwardConsider a copper wire with a diameter of 2.75 mm. A. What is the drift speed of the electrons in the copper wire when a current of 13.0 A flows through it? Assume that each copper atom contributes one free electron to the metal. The density of copper is 8.92 g/cm3. B. How does this drift speed compare to the random rms speed of an electron at 20.0°C? To make this comparison, determine the random rms speed of an electron at 20.0°C using the ideal gas model and find the ratio of the two speeds.arrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning