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3 years ago

Shane's 100-watt radio draws 7 amps of current on a 120-volt circuit. What is the resistance in the radio?

Engineering

1 answer:

Elis [28]3 years ago

7 0

Answer:

Resistance, R = 2.04 Ohms.

Explanation:

Given the following data;

Current = 7 amps

Circuit voltage = 120 Volts

Power = 100 Watts

To find the resistance;

First of all, we would calculate the potential difference (voltage level) used by the radio.

Power = current * voltage

100 = 7 * voltage

Voltage = 100/7

Voltage = 14.29 Volts

Next, we solve for the resistance of the radio;

Ohm's law states that at constant temperature, the current flowing in an electrical circuit is directly proportional to the voltage applied across the two points and inversely proportional to the resistance in the electrical circuit.

Mathematically, Ohm's law is given by the formula;

$V = IR$

Where;

V represents voltage measured in voltage.

I represents current measured in amperes.

R represents resistance measured in ohms.

Substituting into the formula, we have;

$14.29 = 7*R$

$R = \frac {14.29}{7}$

Resistance, R = 2.04 Ohms.

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Answer:

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Explanation:

Use Newton’s law of cooling to determine the heat transfer coefficient. Assume there is no heat transfer from the ends of electric resistor. Heat is transferred from the resistor curved surface.

Step1

Given:

Diameter of the resistor is 2 cm.

Length of the resistor is 16 cm.

Current is 5 amp.

Voltage is 6 volts.

Resistor temperature is 100°C.

Room air temperature is 20°C.

Step2

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Step3

Newton’s law of cooling is expressed as follows:

$Q=h\times \pi DL(T_{r}-T_{\infty})$

Here, h is the convection heat coefficient and $\pi DL$ is the exposed surface area of the resistor.

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