Three resistors of 3.6 ohms, 4.5 ohms, and 6.2 ohms are connected in series to a 120V supply. The circuit current will be:
120V/ 14.3 ohms = 8.39 A
A strip heater consists of four identical elements connected in series to a 240V supply. If the line current is 20 amps, the resistance of each element is:
3 ohms
A 30 ohm, a 10 ohm and a third resistor, that has a volt drop of 60V across it, are all series connected to 120 volts. The voltage drop across the 30 ohm resistor is:
45 Volts
Ten identical resistors are connected in series to a constant voltage source. If one resistor becomes shorted, the total power developed by the circuit will:
Increase
In a parallel circuit, increasing the number of branches will cause the circuit _______ to increase and the circuit ______ to decrease
Resistance, Current
Four identical, parallel connected resistors, dissipate a total of 1.6kW. When reconnected in series, to the same voltage source, each resistor would dissipate:
25 W
The total resistance of two resistors in parallel is 5 ohms. If one of the resistors is 25 ohms, then the other resistor is:
6.25 ohms
Three parallel connected devices draw a total of 48 amps from their source voltage. One of the devices, a lighting unit, dissipates 1.2kW while another device, a motor, draws 8 amps. The third device a heater, dissipates 3.6k W
What is the current drawn by the heater?
What is the resistance of the motor?
The current drawn by the heater is 30 A
The resistance of the motor is 15 ohms.
Which one of the following is suitable as a fire-resistant wiring?
a) Non metallic sheathed cable
b) Armoured cable
c) mineral insulated cable
d) flat conductor cable
c) mineral insulated cable
In “type NMD90” what does the 90 refer to?
It’s temperature
A “tubular” copper conductor has an outside diameter of 1.125 inches and an inside diameter of 0.875 Inches, What is the circular mil area of the copper conductor?
CMA = Dout square - Din square
500,000 CMA
The resistance of a coil of copper write at 0 degrees Celsius is exactly 10 ohms. What is the resistance at 80 degrees Celsius?
13.144 Ohms
A baseboard heater is rated 2.25kW at 120V the conductor supplying the baseboard heater has a resistance of 1.5876 ohms per 1000 feet. The supply voltage is 120V and the maximum permitted drop is 3% of the supply, the maximum one way distance the load can be from the source is:
60.4 feet
A simple three wire circuit has R1 connected to line 1 and the neutral and R2 connected to line 2 and the neutral. Resistor R1 has a greater ohmic value than resistor R2 An open in the neutral conductor would cause:
R1 voltage to increase and the power to increase
in an unbalanced three wire circuit line 1 carries 7 amps and line 2 carries 13 amps. what is the current in the neutral?
Ineutral = I1-I2
7A-13A =-6 A
Answer is 6 amps
A three wire circuit is said to be balanced when:
Two lines currents at the source are equal
For an unbalanced three wire with two 120V
loads, the direction of current in the general conductor is:
a) in the same direction as the largest line current
b) in the same direction as the smallest line current
c) zero and therefore has no direction
d) Not capable of being determined without values being given
b) in the same direction as the smallest line current
