Electricity: Electric Ciruits

Electric Circuits: Audio Guided Solution

Problem 34:

Cullen Ary's family loves to cook. According to Cullen's friends, they have every imaginable kitchen gadget that exists. One Sunday afternoon, they have a cooking party in which every member of the family participates. They get out the following small appliances, plug them in and turn them on.

Mixer (81 Ω)
Crockpot (62 Ω)
Juicer (43 Ω)
Blender (21 Ω)
Electric Fondue (16 Ω)
Wok (12 Ω)
Rotisserie (7.5 Ω)
Deep-fat fryer (7.0 Ω)

The resistance values for each appliance is listed in parenthesis. Each appliance is plugged in to 110-volt receptacles which are wired in parallel on the same circuit. The circuit is protected by a 20-amp circuit breaker.

a. Determine the overall current on the circuit with the mixer and crockpot operating.
b. Determine the overall current on the circuit with the mixer, crockpot and juicer operating.
c. Determine the overall current on the circuit with the mixer, crockpot, juicer and blender operating.
d. Determine the overall current on the circuit with the mixer, crockpot, juicer, blender and electric fondue operating.
e. Determine the overall current on the circuit with the mixer, crockpot, juicer, blender, electric fondue, and wok operating.
f. Determine the overall current on the circuit with the mixer, crockpot, juicer, blender, electric fondue, wok, and rotisserie operating.
g. Determine the overall current on the circuit with the mixer, crockpot, juicer, blender, electric fondue, wok, rotisserie, and the deep-fat fryer operating.
h. At what point in the progression of turning on appliances will the circuit become overloaded and the circuit breaker interrupt the circuit.

Audio Guided Solution

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Habits of an Effective Problem Solver

• Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
• Identify the known and unknown quantities and record them in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., ΔV = 9.0 V; R = 0.025 Ω; I = ???.
• Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
• Identify the appropriate formula(s) to use.
• Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.