EBK PHYSICS FOR SCIENTISTS & ENGINEERS
5th Edition
ISBN: 9780134296074
Author: GIANCOLI
Publisher: VST
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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.
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?
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?
Chapter 29 Solutions
EBK PHYSICS FOR SCIENTISTS & ENGINEERS
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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- The ratio of number of windings on the primary side to the number of windings on the secondary side of a transformer is 10:1. If the voltage on the orimary side is 120V, what would be the voltage on the secondary side?arrow_forwardA transformer has 20 turns of wire in its primary coil and 80 turns on its secondary coil. (a) Is this a step-up or step-down transformer? step-up or step-down (b) If an alternating voltage with an effective voltage of 140.0 V is applied to the primary, what is the effective voltage induced in the secondary? V?arrow_forwardA generator supplies 100 V to a transformer’s primary coil, which has 50 turns. If the secondary coil has 500 turns, what is the secondary voltage?arrow_forward
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