College Physics: A Strategic Approach (3rd Edition)
3rd Edition
ISBN: 9780321879721
Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
Publisher: PEARSON
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Chapter 23, Problem 78GP
Intermittent windshield wipers use a variable resistor in an RC circuit to set the delay between successive passes of the wipers. A typical circuit is shown in Figure P23.78. When the switch closes, the capacitor (initially uncharged) begins to charge and the potential at point b begins to increase. A sensor measures the potential difference between points a and b, triggering a pass of the wipers when Vb = Va. (Another part of the circuit, not shown, discharges the capacitor at this time so that the cycle can start again.)
a. What value of the variable resistor will give 12 seconds from the start of a cycle to a pass of the wipers?
b. To decrease the time, should the variable resistance be increased or decreased?
Figure P23.78
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Chapter 23 Solutions
College Physics: A Strategic Approach (3rd Edition)
Ch. 23 - The tip of a flashlight bulb is touching the top...Ch. 23 - A flashlight bulb is connected to a battery and is...Ch. 23 - Current Iin flows into three resistors connected...Ch. 23 - The circuit in Figure Q23.4 has two resistors,...Ch. 23 - The circuit in Figure Q23.5 has a battery and two...Ch. 23 - In the circuit shown in Figure Q23.6, bulbs A and...Ch. 23 - Figure Q23.7 shows two circuits. The two batteries...Ch. 23 - Figure Q23.8 shows two circuits. The two batteries...Ch. 23 - a. In Figure Q23.9, what fraction of current I...Ch. 23 - Two of the three resistors in Figure Q23.10 are...
Ch. 23 - Two of the three resistors in Figure Q23.11 are...Ch. 23 - Rank in order, from largest to smallest, the...Ch. 23 - The three bulbs in Figure Q23.13 are identical....Ch. 23 - The four bulbs in Figure Q23.14 are identical....Ch. 23 - Figure Q23.15 shows five identical bulbs connected...Ch. 23 - a. The three bulbs in Figure Q23.16 are identical....Ch. 23 - Initially, bulbs A and B in Figure Q23.17 are both...Ch. 23 - a. Consider the points a and b in Figure Q23.18....Ch. 23 - When the switch in Figure Q23.19 is closed, a....Ch. 23 - A voltmeter is (incorrectly) inserted into a...Ch. 23 - An ammeter is (incorrectly) inserted into a...Ch. 23 - Rank in order, from largest to smallest, the...Ch. 23 - Figure Q23.23 shows a circuit consisting of a...Ch. 23 - Figure Q23.24 shows the volt age as a function of...Ch. 23 - A charged capacitor could be connected to two...Ch. 23 - A flashing light is controlled by the charging and...Ch. 23 - A device to make an electrical measurement of skin...Ch. 23 - Consider the model of nerve conduction in...Ch. 23 - Adding a myelin sheath to an axon results in...Ch. 23 - What is the current in the circuit of Figure...Ch. 23 - Which resistor in Figure Q23.30 dissipates the...Ch. 23 - Normally, household lightbulbs are connected in...Ch. 23 - A metal wire of resistance R is cut into two...Ch. 23 - What is the value of resistor R in Figure Q23.34?...Ch. 23 - Two capacitors are connected in series. They are...Ch. 23 - If a cells membrane thickness doubles but the cell...Ch. 23 - If a cells diameter is reduced by 50% without...Ch. 23 - Draw a circuit diagram tor the circuit of Figure...Ch. 23 - Draw a circuit diagram for the circuit of Figure...Ch. 23 - Draw a circuit diagram for the circuit of Figure...Ch. 23 - In Figure P23.4, what is the current in the wire...Ch. 23 - The lightbulb in the circuit diagram of Figure...Ch. 23 - a. What are the magnitude and direction of the...Ch. 23 - a. What are the magnitude and direction of the...Ch. 23 - a. What is the potential difference across each...Ch. 23 - The current in a circuit with only one battery is...Ch. 23 - What is the equivalent resistance of each group of...Ch. 23 - What is the equivalent resistance of each group of...Ch. 23 - Prob. 12PCh. 23 - Prob. 13PCh. 23 - You have a collection of 1.0 k resistors. How can...Ch. 23 - You have a collection of six 1.0 k resistors. What...Ch. 23 - You have six 1.0 k resistors. How can you connect...Ch. 23 - What is the equivalent resistance between points a...Ch. 23 - What is the equivalent resistance between points a...Ch. 23 - The currents in two resistors in a circuit are...Ch. 23 - Two batteries supply current to the circuit in...Ch. 23 - Part of a circuit is shown in Figure P23.21. a....Ch. 23 - What is the value of resistor R in Figure P23.22?...Ch. 23 - What are the resistances R and the emf of the...Ch. 23 - The ammeter in Figure P23.24 reads 3.0 A. Find I1,...Ch. 23 - Find the current through and the potential...Ch. 23 - Find the current through and the potential...Ch. 23 - For the circuit shown in Figure P23.27, find the...Ch. 23 - Consider the potential differences between pairs...Ch. 23 - For the circuit shown in Figure P23.29, find the...Ch. 23 - A photoresistor, whose resistance decreases with...Ch. 23 - The two unknown resistors in Figure P23.31 have...Ch. 23 - A 6.0 F capacitor, a 10 F capacitor, and a 16 F...Ch. 23 - A 6.0 F capacitor, a 10 F capacitor, and a 16 F...Ch. 23 - You need a capacitance of 50 F, but you dont...Ch. 23 - You need a capacitance of 50 F, but you dont...Ch. 23 - What is the equivalent capacitance of the three...Ch. 23 - What is the equivalent capacitance of the three...Ch. 23 - For the circuit of Figure P23.38, a. What is the...Ch. 23 - For the circuit of Figure P23.39. a. What is the...Ch. 23 - What is the time constant for the discharge of the...Ch. 23 - What is the time constant for the discharge of the...Ch. 23 - After how many time constants has the voltage...Ch. 23 - A 10F capacitor initially charged to 20C is...Ch. 23 - A capacitor charging circuit consists of a...Ch. 23 - The switch in Figure P23.45 has been in position a...Ch. 23 - A 9.0-nm-thick cell membrane undergoes an action...Ch. 23 - A cell membrane has a resistance and a capacitance...Ch. 23 - Changing the thickness of the myelin sheath...Ch. 23 - A particular myelinated axon has nodes spaced 0.80...Ch. 23 - To measure signal propagation in a nerve in the...Ch. 23 - A myelinated axon conducts nerve impulses at a...Ch. 23 - How much power is dissipated by each resistor in...Ch. 23 - Two 75 W (120 V) lightbulbs are wired in series,...Ch. 23 - The corroded contacts in a lightbulb socket have...Ch. 23 - A real battery is not just an emf. We can If model...Ch. 23 - For the real battery shown in Figure P23.55,...Ch. 23 - Batteries are recharged by connecting them to a...Ch. 23 - When two resistors are connected in parallel...Ch. 23 - The 10 resistor in Figure P23.59 is dissipating 40...Ch. 23 - At this instant the current in the circuit of...Ch. 23 - What is the equivalent resistance between points a...Ch. 23 - What is the current through the battery in Figure...Ch. 23 - What is the ratio P parallel/P series of the total...Ch. 23 - You have a device that needs a voltage reference...Ch. 23 - There is a current of 0.25 A in the circuit of...Ch. 23 - A circuit youre building needs an ammeter that...Ch. 23 - A circuit youre building needs a voltmeter that...Ch. 23 - For the circuit shown in Figure P23.68, find the...Ch. 23 - You have three 12 F capacitors. Draw diagrams...Ch. 23 - Initially, the switch in Figure P23.70 is in...Ch. 23 - The capacitor in an RC circuit with a time...Ch. 23 - The capacitor in Figure P23.72 is initially...Ch. 23 - What value resistor will discharge a 1.0 F...Ch. 23 - The charging circuit for the flash system of a...Ch. 23 - A capacitor is discharged through a 100 resistor....Ch. 23 - A 50 /F capacitor that had been charged to 30 V is...Ch. 23 - The switch in Figure P23.77 has been closed for a...Ch. 23 - Intermittent windshield wipers use a variable...Ch. 23 - In Example 23.14 we estimated the capacitance of...Ch. 23 - The giant axon of a squid is 0.5 mm in diameter,...Ch. 23 - A cell has a 7.0-nm-thick membrane with a total...Ch. 23 - The Defibrillator A defibrillator is designed to...Ch. 23 - The Defibrillator A defibrillator is designed to...Ch. 23 - The Defibrillator A defibrillator is designed to...Ch. 23 - A defibrillator is designed to pass a large...Ch. 23 - The voltage produced by a single nerve or muscle...Ch. 23 - The voltage produced by a single nerve or muscle...Ch. 23 - The voltage produced by a single nerve or muscle...Ch. 23 - The voltage produced by a single nerve or muscle...
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