Exam 8: Formulas

If the cross-sectional area of a wire is 16,510 circular mils, what is the diameter (d) of the wire? Carry the answer to two decimal places. Cross-sectional area = $d ^ { 2 }$ where d = diameter in mils

Find the total resistance ( $R _ { T }$ ) of the circuit shown.

A motor takes a current of 8 amps per leg on a 440-volt, 3-phase circuit. The power factor is 0.75. What is the load in watts? Carry the answer to two decimal places. $P = \sqrt { 3 } ( E ) ( I ) ( P F )$

Choose the correct formula to solve the problem. $O P = V _ { 1 } ^ { 2 } + V _ { 2 } ^ { 2 } + 2 \left( V _ { 1 } \right) \left( V _ { 2 } \right) \cos \theta$ $I = E / R$ $E = I R$ $R = E / I$ $P = I ^ { 2 } R$ $I = P / E$ $E = P / I$ $R = E ^ { 2 } / p$ $P = E ^ { 2 } / R$ $I = \sqrt { P / R }$ $E = \sqrt { P R }$ $R = P / I _ { I ^ { 2 } }$ A one-horsepower motor uses 900 watts when connected to a circuit. The motor receives a current of 3.4 amps. Find the voltage to one decimal place that is across the circuit.

A three-phase, three-wire circuit delivers 175 amperes at a voltage of 220 volts with a 0.85 power factor. What is the kilowatt load to the nearer hundredth? k W load = where k W load = 3-phase power in kilowatts i = current in amperes X = voltage involts P F = power factor

Choose the correct formula to solve the problem. $O P = V _ { 1 } ^ { 2 } + V _ { 2 } ^ { 2 } + 2 \left( V _ { 1 } \right) \left( V _ { 2 } \right) \cos \theta$ $I = E / R$ $E = I R$ $R = E / I$ $P = I ^ { 2 } R$ $I = P / E$ $E = P / I$ $R = E ^ { 2 } / p$ $P = E ^ { 2 } / R$ $I = \sqrt { P / R }$ $E = \sqrt { P R }$ $R = P / I { ^ { 2 } }$ A 550-watt electric iron has a voltage drop of 112 volts. What current to the nearer hundredth amp exists in the iron?

Find the power used in the single-phase circuit shown. Carry the answer to three decimal places. $X _ { L }$

Find the impedance of a coil with 5.5 ohms resistance and 8.2 ohms reactance. Round the answer to the nearer hundredth.

If $E _ { a }$ is the unknown resistance of the Wheatstone bridge arrangement shown in the figure, find the value of this unknown resistance. Carry the answer to one decimal place. $E_ b$

The electrostatic force ( F ) between two plates of a charged capacitor is directly proportional to the product of the charges ( $q_ 1$ and $q_2$ ) on each plate and inversely proportional to the square of the distance ( d ) between the plates.

What current will exist in a 3,000-watt electric iron when a voltage of 240 volts is maintained? Carry the answer to one decimal place. $I = P / E$

Choose the correct formula to solve the problem. $O P = V _ { 1 } ^ { 2 } + V _ { 2 } ^ { 2 } + 2 \left( V _ { 1 } \right) \left( V _ { 2 } \right) \cos \theta$ $I = E / R$ $E = I R$ $R = E / I$ $P = I ^ { 2 } R$ $I = P / E$ $E = P / I$ $R = E ^ { 2 } / p$ $P = E ^ { 2 } / R$ $I = \sqrt { P / R }$ $E = \sqrt { P R }$ $R = P / I _ { I ^ { 2 } }$ A circuit has a voltage of 120 volts and a current of 7.5 amps. Find the amount of power used.