The total current delivered to a number of devices connected in parallel is the sum of the individual currents in each device. Circuit breakers are resettable automatic switches that protect against a dangerously large total current by "opening" to stop the current at a specified safe value. A 1620-W toaster, a 1150-W iron, and a 969-W microwave oven are turned on in a kitchen. As the drawing shows, they are all connected through a 20-A circuit breaker (which has negligible resistance) to an ac voltage of 120 V. (a) Find the equivalent resistance of the three devices. (b) Obtain the total current delivered by the source and (c) determine whether the breaker will "open" to prevent an accident (yes or no). Circuit breaker 20 A 120 V (a) Number Units (b) Number Units (c)

The total current delivered to a number of devices connected in parallel is the sum of the individual currents in each device. Circuit breakers are resettable automatic switches that protect against a dangerously large total current by "opening" to stop the current at a specified safe value. A 1620-W toaster, a 1150-W iron, and a 969-W microwave oven are turned on in a kitchen. As the drawing shows, they are all connected through a 20-A circuit breaker (which has negligible resistance) to an ac voltage of 120 V. (a) Find the equivalent resistance of the three devices. (b) Obtain the total current delivered by the source and (c) determine whether the breaker will "open" to prevent an accident (yes or no). Circuit breaker 20 A 120 V (a) Number Units (b) Number Units (c)

College Physics

10th Edition

ISBN:9781285737027

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter17: Current And Resistance

Section: Chapter Questions

Problem 22P: The human body can exhibit a wide range of resistances to current depending on the path of the...

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(a) A defibrillator sends a 6.00-A current through the chest of a patient by applying a 10,000-V potential as in the figure below. What is the resistance of the path? (b) The defibrillator paddles make contact with the patient through a conducting gel that greatly reduces the path resistance. Discuss the difficulties that would ensue if a larger voltage were used to produce the same current through the patient, but with the path having perhaps 50 times the resistance. (Hint: The current must be about the same, so a higher voltage would imply greater power. Use this equation for power: P=I2 RP = .)
The human body can exhibit a wide range of resistances to current depending on the path of the current, contact area, and sweatiness of the skin. Suppose the resistance across the chest from the left hand to the right hand is 1.0 106 . (a) How much voltage is required to cause possible heart fibrillation in a man, which corresponds to 500 mA of direct current? (b) Why should rubber-soled shoes and rubber gloves be worn when working around electricity?
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A toaster using a Nichrome heating element operates on 120 V. When it is switched on at 24∘С, the heating element carries an initial current of 1.38 A. A few seconds later the current reaches the steady value of 1.23 A. What physical process is launched with the switching on of the toaster? Why does the current decrease from its initial value and reach another steady value? Choose the best answer from below. A. When switched on, heating element of the toaster acts as a parallel connection of a resistor and an inductor. This connection reacts to any change of the current with a delay. As the result, current initially increases to a greater value and then reaches the saturated value. B. When switched on, heating element of the toaster acts as a resistor and converts electrical energy into thermal. However, there are imperfections in the circuit that lead to a loss of energy. As the result, amount of the current that is transformed to thermal energy decreases. C. When…
A heart defibrillator is used to enable the heart to start beating if it has stopped. This is done by passing a large current of 12 A through the body at 25 V for a very short time, usually about 3 millisecond. How much energy is transferred from the defibrillator to the body?
A heart defibrillator is used to enable the heart to start beating if it has stopped. This is done by passing a large current of 12 A through the body at 25 V for a very short time, usually about 3 milliseconds. How much energy is transferred from the defibrillator to the body?