Exam 8: Formulas

$E _ { L I N E } = \sqrt { E _R ^ { 2 } + E _X ^ { 2 } }$ The four dry cells are connected in series as shown. Find the total resistance. Carry the answer to three decimal places.

The total capacitance ( C ) is directly proportional to the product of the dielectric constant ( k ) and plate area ( A ) and inversely proportional to the thickness ( d ) of the dielectric.

Find the number of watts in the armature of a generator having an internal resistance of 0.3 ohm and a voltage of 6 volts across the resistance. $P = E ^ { 2 } / R$

$E _ { L I N E } = \sqrt { E_ R ^ { 2 } + E_ X ^ { 2 } }$ A lamp with a resistance (hot) of 50 ohms is connected across 120 volts. What current does the lamp receive?

$E _ { L I N E } = \sqrt { E _R ^ { 2 } + E _X ^ { 2 } }$ A 60-volt electric time clock circuit with several clocks connected in parallel has a 2-wire line voltage drop of 12.5 volts when the circuit is closed. Using Ohm s law, find the total resistance of the 2-wire line if a current of 10 amps exists. Carry the answer to two decimal places.

The resonant frequency ( $f _ { r }$ ) of a circuit containing both inductance ( L ) and capacitance ( C ) may be found by the reciprocal of two pi ( $2 \pi$ ) Hint:((The reciprocal is 1/ $2 \pi$ )) multiplied by the square root of the product of the inductance and capacitance.

The internal resistance of five cells is 1.8 ohms each. The cells are connected as shown in the diagram to a 2-ohm resistance. What current, to the nearer hundredth, exists in the circuit? $E_ X$

The temperature of a motor rises to $E _ { C }$ C above room temperature. The room temperature is $E_ b$ C. What will a Fahrenheit thermometer read? Carry the answer to one decimal place. $E _ { a }$

What is the impedance ( Z ) of a coil with 84 ohms resistance ( R ) and 500 ohms reactance (X)? Round the answer to the nearer ohm. $Z = \sqrt { R ^ { 2 } + X ^ { 2 } }$

$E _ { L I N E } = \sqrt { E_ R ^ { 2 } + E_ X ^ { 2 } }$ What voltage is required to force a 4.5-amp current through an electric iron having a resistance of 25.5 ohms?

Choose the correct formula to solve the problem. $O P = V _ { 1 } ^ { 2 } + V _ { 2 } ^ { 2 } + 2 \left( V _ { 1 } \right) \left( V _ { 2 } \right) \cos \theta$ $I = E / R$ $E = I R$ $R = E / I$ $P = I ^ { 2 } R$ $I = P / E$ $E = P / I$ $R = E ^ { 2 } / p$ $P = E ^ { 2 } / R$ $I = \sqrt { P / R }$ $E = \sqrt { P R }$ $R = P / I _ { I ^ { 2 } }$ How many watts will a motor use if the voltage is 240 volts and the motor is drawing 40 amps of current?

$E _ { L I N E } = \sqrt { E _R ^ { 2 } + E _X ^ { 2 } }$ What is the current in amperes in a 3-phase circuit when the load is 67.5 horsepower, the efficiency is 90%, the voltage is 440 volts, and the circuit power factor is 0.80? Round the answer to the nearer hundredth. $h p = \frac { \sqrt { 3 } ( E ) ( I ) ( E f f ) ( P F ) } { 746 }$

$E _ { L I N E } = \sqrt { E _R ^ { 2 } + E _X ^ { 2 } }$ A lamp requires a current of 0.94 amps when connected to a circuit with a voltage of 120 volts. Find the resistance in ohms of the lamp. Carry the answer to two decimal places.

An electrical motor has a degree of efficiency ( Eff ) equal to the ratio of its useful output power ( $P _ { 0 }$ ) to the input power ( $p _ { 1 }$ ) required to operate it.

If a current of 4.5 amperes exists, what is the impedance of a circuit having a voltage of 110 volts across it? Express the answer to the nearer hundredth. Z= where Z= impedance in ohms E= voltage in volts I = current in amperes

$E _ { L I N E } = \sqrt { E _R ^ { 2 } + E _X ^ { 2 } }$ One 2-wire section of a 24-volt watchman clock signal system is operated through a 450-foot length of lead covered cable drawing 2 amps. The size of the conductor is number 18, and the diameter is 40.3 mils. What is the resistance of one conductor? Express the answer to the nearer whole number. CM= where N= number of wires K= constant (10.8) L= length of one wire infeet R= resistance in ohms d= diameter in mils

A motor takes a current of 27.5 amperes per leaf on a 440-volt, three-phase circuit. The power factor is 0.80. What is the load in watts? Round the answer to the nearer whole watt. For a three-phase circuit: $I _ { S }$

Choose the correct formula to solve the problem. $a ^ { 2 } = b ^ { 2 } + c ^ { 2 }$ $E = I R$ $R = E / I$ What voltage will be required to create a current of 5 milliamps through a wire-wound resister having a resistance of 750 ohms? Carry the answer to two decimal places.

Solve the equation for the current ( I ) required by a motor when the horsepower, percent efficiency of the motor, and the voltage are known. hp= where l= current in amperes E= voltage in volts Eff= efficiency of motor hp= horsepower

A circuit uses 216.2 watts and draws a current of 1.88 amps. Find the resistance. Express the answer to the nearer hundredth ohm. $E = P / I$ and $R = E / I$