1. A) An electrical device with a resistance of 5.0 ? will allow a current of 12

Question

1.     A) An electrical device with a resistance of 5.0 ? will allow a current of 12 amps to flow through it if a voltage drop of _____ V is impressed across the device.

2.    B) A flashlight that is powered by 9V and uses a bulb with a resistance of 120 ? will have a current of ______ amps.

3.   C) When a potential difference of 12V is applied to a wire 6.9m long and .33mm in diameter, the result is an electric current of 2.1 A. What is the resistivity of the wire?

4.   D) A power saw at the local hardware store boasts of having a 15-Amp motor. Determine its resistance when plugged into a 110-Volt outlet.

1.   E) Three resistors with resistance values of 2-ohms , 4-ohms , and 6-ohms are placed in series. These would provide a resistance which is equivalent to one _____ resistor.

2.   F) Three 8-ohms resistors placed in parallel would provide a resistance which is equivalent to one _____ resistor.

Explanation / Answer

1). V = I*R = 12*5 = 60 2). I = 9/120 = 0.075 3). R = V/I = 12/2.1 = 5.714 ohm R = p*(L/A) => 5.714 = p*[6.9*4/{3.14*(0.33*10^-3)^2}] = 7.08*10^-8 ohm-m 4). R = V/I = 110/15 = 7.33 ohm E). 2+4+6 = 12 ohm F). 8/3 ohm G). 1/R = (1/5) + (1/6) + (1/7) => R = 1.963 ohm

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