College Physics
1st Edition
ISBN: 9781938168000
Author: Paul Peter Urone, Roger Hinrichs
Publisher: OpenStax College
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Textbook Question
Chapter 21, Problem 24CQ
Why should you not connect an ammeter directly across a voltage source as shown in Figure 21.48? (Note that script E in the figure stands for emf.)
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9. (A) Consider the circuit in Figure on the right and assume the battery has
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time constant of the capacitor, what will the current be in the 2-2 resistor?
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Why should you not connect an ammeter directly across a voltage source as shown in Figure 21.51? (Note that script E in the figure stands for emf.)
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Chapter 21 Solutions
College Physics
Ch. 21 - A switch has a variable resistance that is nearly...Ch. 21 - What is the voltage across the open switch in...Ch. 21 - There is a voltage across an open switch, such as...Ch. 21 - Why is the power dissipated by a closed switch,...Ch. 21 - A student in a physics lab mistakenly wired a...Ch. 21 - Knowing that the severity of a shock depends on...Ch. 21 - Would your headlights dim when you start your...Ch. 21 - Some strings of holiday lights are wired in series...Ch. 21 - If two household lightbulbs rated 60 W and 100 W...Ch. 21 - Suppose you are doing a physics lab that asks you...
Ch. 21 - Before World War II, some radios got power through...Ch. 21 - Some light bulbs have three power settings (not...Ch. 21 - Is every emf a potential difference? Is every...Ch. 21 - Explain which battery is doing the charging and...Ch. 21 - Given a battery, an assortment of resistors, and a...Ch. 21 - Two different 12-V automobile batteries on a store...Ch. 21 - What are the advantages and disadvantages of...Ch. 21 - Semitractor trucks use four large 12-V batteries....Ch. 21 - Call all of the currents going into the junction...Ch. 21 - Apply the junction rule to junction b in Figure...Ch. 21 - (a) What is the potential difference going from...Ch. 21 - Apply the loop rule to loop afedcba in Figure...Ch. 21 - Apply the loop rule to loops abgefa and cbgedc in...Ch. 21 - Why should you not connect an ammeter directly...Ch. 21 - Suppose you are using a multimeter (one designed...Ch. 21 - Specify the points to which you could connect a...Ch. 21 - To measure currents in Figure 21.49, you would...Ch. 21 - Why can a null measurement be more accurate than...Ch. 21 - If a potentiometer is used to measure cell emfs on...Ch. 21 - Regarding the units involved in the relationship t...Ch. 21 - The RC time constant in heart defibrillation is...Ch. 21 - When making an ECG measurement, it is important to...Ch. 21 - Draw two graphs of charge versus time on a...Ch. 21 - When charging a capacitor, as discussed in...Ch. 21 - When discharging a capacitor, as discussed in...Ch. 21 - Referring to Figure 21.38, draw a graph of...Ch. 21 - A long, inexpensive extension cord is connected...Ch. 21 - In Figure 21.41. does the graph indicate the time...Ch. 21 - An electronic apparatus may have large capacitors...Ch. 21 - (a) What is the resistance often 275-O resistors...Ch. 21 - (a) What is the resistance of a 1.00 102-O, a...Ch. 21 - What are the largest and smallest resistances you...Ch. 21 - An 1800-W toaster, a 1400-W electric frying pan,...Ch. 21 - Your car’s 30.0-W headlight and 2.40-kW starter...Ch. 21 - (a) Given a48.0-V battery and 24.0-O and 96.0-O...Ch. 21 - Referring to the example combining series and...Ch. 21 - Referring to Figure 21.6: (a) Calculate P3 and...Ch. 21 - Refer to Figure 21.7 and the discussion of lights...Ch. 21 - A 240-kV power transmission line carrying...Ch. 21 - Show that if two resistors R1and R2are combined...Ch. 21 - Unreasonable Results Two resistors, one having a...Ch. 21 - Unreasonable Results Two resistors, one having a...Ch. 21 - Standard automobile batteries have six lead-acid...Ch. 21 - Car bon-zinc dry cells (sometimes referred to as...Ch. 21 - What is the output voltage of a 3.0000-V lithium...Ch. 21 - (a) What is the terminal voltage of a large 1.54-V...Ch. 21 - What is the internal resistance of an automobile...Ch. 21 - (a) Find the terminal voltage of a 12.0-V...Ch. 21 - A car battery with a 12-V emf and an internal...Ch. 21 - The hot resistance of a flashlight bulb is 2.30 ,...Ch. 21 - The label or a portable radio recommends the use...Ch. 21 - An automobile starter motor has an equivalent...Ch. 21 - A child’s electronic toy is supplied by three...Ch. 21 - (a) What is the internal resistance of a voltage...Ch. 21 - A person with body resistance between his hands of...Ch. 21 - Electric fish generate current with biological...Ch. 21 - Integrated Concepts A 12.0-V emf automobile...Ch. 21 - Unreasonable Results A 1.58-V alkaline cell with a...Ch. 21 - Unreasonable Results (a) What is the internal...Ch. 21 - Apply the loop rule to loop abcdefgha in Figure...Ch. 21 - Apply the loop rule to loop aedcba in Figure...Ch. 21 - Verify the second equation in Example 21.5 by...Ch. 21 - Verify the third equation in Example 21.5 by...Ch. 21 - Apply the junction rule at point a in Figure...Ch. 21 - Apply the loop rule to loop abcdefghija in Figure...Ch. 21 - Apply the loop rule to loop akledcba in Figure...Ch. 21 - Find the currents flowing in the circuit in Figure...Ch. 21 - Solve Example 21.5, but use loop abcdefgha instead...Ch. 21 - Find the currents flowing in the circuit in Figure...Ch. 21 - Unreasonable Results Consider the circuit in...Ch. 21 - What is the sensitivity of the galvanometer (that...Ch. 21 - What is the sensitivity of the galvanometer (that...Ch. 21 - Find the resistance that must be placed in series...Ch. 21 - Find the resistance that must be placed in series...Ch. 21 - Find the resistance that must be placed in series...Ch. 21 - Find the resistance that must be placed in...Ch. 21 - Find the resistance that must be placed in series...Ch. 21 - Find the resistance that must be placed in...Ch. 21 - Suppose you measure the terminal voltage of a...Ch. 21 - Suppose you measure the terminal voltage of a...Ch. 21 - A certain ammeter has a resistance of 5.00X10-5 ...Ch. 21 - A 1,00-?O voltmeter is placed in parallel with a...Ch. 21 - A 0.0200- ammeter is placed in series with a...Ch. 21 - Unreasonable Results Suppose you have a 40.0-...Ch. 21 - Unreasonable Results (a) What resistance would you...Ch. 21 - What is the emf x of a cell being measured in a...Ch. 21 - Calculate the emfx of a dry cell for which a...Ch. 21 - When an unknown resistance Rxis placed in a...Ch. 21 - To what value must you adjust R3to balance a...Ch. 21 - (a) What is the unknown emfx in a potentiometer...Ch. 21 - Suppose you want to measure resistances in the...Ch. 21 - The timing device in an automobile’s intermittent...Ch. 21 - A heart pacemaker fires 72 times a minute, each...Ch. 21 - The duration of a photographic flash is related to...Ch. 21 - A 2.00- and a 7.50-F capacitor can be connected in...Ch. 21 - After two time constants, what percentage of the...Ch. 21 - A 500- resistor, an uncharged 1.50-F capacitor and...Ch. 21 - A heart defibrillator being used on a patient has...Ch. 21 - An ECG monitor must have an RC time constant less...Ch. 21 - Figure 21.55 shows how a bleeder resistor is used...Ch. 21 - Using the exact exponential treatment, find how...Ch. 21 - Using the exact exponential treatment, find how...Ch. 21 - Integrated Concepts If you wish to take a picture...Ch. 21 - Integrated Concepts A flashing lamp in a Christmas...Ch. 21 - Integrated Concepts A 160F capacitor charged to...Ch. 21 - Unreasonable Results (a) Calculate the capacitance...Ch. 21 - Construct Your Own Problem Consider a camera's...Ch. 21 - Construe! Your Own Problem Consider a rechargeable...
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- Figure P18.26 shows a voltage divider, a circuit used to obtain a desired voltage Vout from a source voltage . Determine the required value of R2 if = 5.00 V, Vout = 1.50 V and R1 = 1.00 103 (Hint: Use Kirchhoff's loop rule, substituting Vout = IR2, to find the current. Then solve Ohms law for R2. Figure P18.26arrow_forwardFigure P18.26 shows a voltage divider, a circuit used to obtain a desired voltage Vout from a source voltage . Determine the required value of R2 if = 5.00 V, Vout = 1.50 V and R1 = 1.00 103 (Hint: Use Kirchhoff's loop rule, substituting Vout = IR2, to find the current. Then solve Ohms law for R2. Figure P18.26arrow_forwardIntegrated Concepts 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?arrow_forward
- The power dissipated in a resistor is given by P = V2/R, which means power decreases if resistance increases. Yet this power is also given by P = I2R, which means power increases if resistance increases. Explain why there is no contradiction here.arrow_forwardWhy is it possible for a bird to sit on a high-voltage wire without being electrocuted?arrow_forwardCheck Your Understanding Digital meters are able to detect smaller currents than analog meters employing galvanometers. How does this explain their ability to measure voltage and current more accurately than analog meters?arrow_forward
- When resistors with different resistances are connected in parallel, which of the following must be the same for each resistor? Choose all correct answers, (a) potential difference (b) current (c) power delivered (d) charge entering each resistor in a given time interval (e) none of those answersarrow_forwardFor the two resistors shown in Figure 17.12, rank the currents at points a through f from largest to smallest. (a) Ia = Ib Ie = If Ic = Id (b) Ia= Ib Ic = Id Ie = If (c) Ie = If Ic = Id Ia = Ib Figure 17.12 (Quick Quiz 17.8)arrow_forwardFigure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic device is shut off allowing a person to work on the electronics with less risk of shock, (a) What is the time constant? (b) How long will it take to reduce the voltage on the capacitor to 0.250% (5% of 5%) of its full value once discharge begins? (c) If the capacitor is charged to a voltage V0through a 100-O resistance, calculate the time it takes to rise to 0.865V0(This is about two time constants.)arrow_forward
- A battery applies an EMF of 30 V and has an internal resistance of 1.6 Ohms. The battery is connected to three 9.7 Ohm resistors in parallel with eachother. What is the voltage drop across one of the resistors? Answer in volts. Question 7 options: A) 6.21E+00 B) 9.48E+00 C) 2.58E+01 D) 3.00E+01 E) 2.01E+01 F) 9.77E-01 G) 9.28E+00 H) None of these answers. Two straight wires of length 2.75 m, carrying identical 21 A currents lie parallel to eachother on a table top and carry antiparallel currents. The wires are separated by 25 cm. What is the magnitude of the force between the wires? Answer in Newtons. Question 8 options: A) 9.70E-04 B) 4.62E-05 C) 9.70E-06 D) 0.00E+00 E) 3.53E-04 F) 3.53E+03 G) 6.10E-03 H) None of these answers.arrow_forwardAn 1800 W toaster, a 1420 W electric frying pan, and a 70 W lamp are plugged into the same outlet in a 15 A, 120 V circuit. (The three devices are in parallel when plugged into the same socket.) In your notebook, draw a circuit diagram woth the toaster, frying pan, and lamp. Label the currents passing through each device? Things to prepare: For a parallel connection, what quantity (voltage, current or resistance) is same for all devices? For a parallel connection, what quantities (voltage, current or resistance) are different for the devices? (a) What current is drawn by each device? Itoaster A Ipan Tamp = (b) Will this combination blow the 15 A fuse? Yes No A Aarrow_forwardThe figure shows an LED, protected by a resistor R, which is powered by a 9 Volt battery. If the power of the LED is 70 milliwatts and the voltage drop across the LED is 3.5 volts, determine the value of the resistor R in ohms that should be used in the circuit.arrow_forward
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