Modified Mastering Physics without Pearson eText-- Instant Access -- for Physics for Scientists & Engineers with Modern Physics
5th Edition
ISBN: 9780134402659
Author: GIANCOLI, Douglas
Publisher: PEARSON
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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?
consider a simple transformer that has a 100 turn primary coil and a 1000 turn secondary coil. The primary is connected to 120 volts ac source and the secondary is connected to an electrical device with a resistance of 200 ohms.
what will be the voltage output of the secondary?
what current flows in the secondary circuit?
now that you know the voltage and the current, what is the power in the secondary coil?
neglecting small heating losses, and knowing that energy is conserved, what is the power in the primary coil?
now that you know the power and the voltage across the primary coil, what is the current drawn by the primary coil?
Chapter 29 Solutions
Modified Mastering Physics without Pearson eText-- Instant Access -- for Physics for Scientists & Engineers with Modern Physics
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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