Modified Mastering Physics with Pearson eText -- Combo Access -- for Physics for Scientist and Engineers (18 week)
5th Edition
ISBN: 9780137504299
Author: Douglas C. Giancoli
Publisher: Pearson Education (US)
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Chapter 29, Problem 65GP
A high-intensity desk lamp is rated at 35 W but requires only 12 V. It contains a transformer that converts 120-V household voltage. (a) Is the transformer step-up or step-down? (b) What is the current in the secondary coil when the lamp is on? (c) What is the current in the primary coil? (d) What is the resistance of the bulb when on?
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Ex.3-Cell phone charger. The charger for a cell phone contains a transformer that reduces 120-
V (or 240-V) ac to 5.0-V ac to charge the 3.7-V battery. (It also contains diodes to change the
5.0-V ac to 5.0-V dc.) Suppose the secondary coil contains 30 turns and the charger supplies
700mA. Calculate (a) the number of turns in the primary coil, (b) the current in the primary,
and (c) the power transformed.
A step-up transformer is designed so that the output of its secondary winding is 240 V when
the primary winding is connected to a 120-V line voltage.
(a) If there are 100 turns in the primary winding, how many turns are there in the secondary
winding?
(b) If the coffee grinder in an espresso machine connected across the secondary winding has
a power rating of 240W, what is the current in the primary winding?
An induction coil in an automobile is much like an ac transformer that boosts low voltage to
high. The 12 V from the battery is dc, so a device interrupts the current on and off, producing
a changing current equivalent to ac. Find the ration of primary to secondary turns to boost
12 V to 24,000V required for the spark plugs.
down) from
6.
Chapter 29 Solutions
Modified Mastering Physics with Pearson eText -- Combo Access -- for Physics for Scientist and Engineers (18 week)
Ch. 29 - Prob. 1QCh. 29 - What is the difference between magnetic flux and...Ch. 29 - Suppose you are holding a circular ring of wire...Ch. 29 - The use of higher-voltage lines in homessay, 600 V...Ch. 29 - (II) (a) If the resistance of the resistor in Fig....Ch. 29 - Prob. 30PCh. 29 - (III) A short section of wire, of length a, is...Ch. 29 - (I) Neon signs require 12 kV for their operation....Ch. 29 - Prob. 62GPCh. 29 - Show that the power loss in transmission lines,...
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