A1 LT8 Flashcards
What will happen to current if the applied voltage is decreased to half of its previous value?
Current will also decrease to half of its previous value.
What is the modified version of scientific notation used in the electrical trade?
Engineering notation
To multiply a number by 10^3 in scientific notation, how do you move the decimal point?
Three places to the right
How can the relationship between power, voltage, and current be stated mathematically?
Power is directly proportional to the square of the voltage and current.
What is the main way to solve electrical circuit problems?
By applying Ohm’s and Watt’s laws
What does inversely proportional mean in terms of resistance and current?
If the resistance is doubled, the current will decrease to half of its previous value.
In engineering notation, what kind of exponents are used with powers of 10?
Multiples of three
How do you express 0.057 mA in terms of A?
57 ?A
What is power?
Rate of doing work or energy transfer
What is the abbreviation for the power loss in conductors?
P = I^2 x R
What does Watt’s law state?
Power in a circuit equals the product of the voltage and the current.
What does the kilo represent?
10
What is 5600 milliohms expressed in kilohms?
0.0056 k?
What does voltage measure?
Amount of energy possessed by an electron
What does PR loss refer to?
Power loss as I^2 x R
What is Watt’s law?
P = E x I
What is the formula provided for power?
P = 1R
What is the resistance of a baseboard heater connected to a 240 V source producing heat at the rate of 1500 W?
38.4
At what rate would heat be dissipated if a heater with the same resistance was connected to a 120 V source?
375 W
What is one of the forms in which Ohm’s law can be expressed?
E=I x R
How do you convert milliohms to kilohms?
Move the decimal point six places to the left
What does horsepower refer to?
Amount of work the motor delivers on the shaft
What is the efficiency of a motor?
Ratio of output watts to input watts at rated load
What does motor efficiency represent?
How much of the input power is converted to useful output power
For a 10 HP motor operating at 75% efficiency, how many input watts are drawn by the motor?
9947 watts input
How to determine the HP a motor is delivering on the shaft if it is drawing 3730 watts at rated load?
5 HP
What happens to the current in a circuit if the voltage doubles?
Current also doubles.
What is the formula for voltage?
E=I x R
What is the formula for resistance?
R=E/I
What is the formula for current?
I=E/R
How can Watt’s law be transposed?
E=P/I
How does the power change when voltage doubles in a circuit?
Power also doubles.
What other form can Watt’s law be transposed to?
P=E x I
How can 25,000 volts be written in engineering notation?
25 kV
What effect does increasing the rate of electron flow have on a resistive device?
It becomes warmer due to more collisions and energy transfer.
What happens to the power if both the voltage and current double in a circuit?
Power increases by four times.
How much current would a 200 W light bulb draw from the same 120 V source?
1.67 A
What is the formula to calculate percent efficiency of a motor?
100% efficiency = (output power / input power) x 100
How does power change with an increase in current?
Increases
What is the value of power when resistance is 80 and current is 0.03?
= 192 W
