AC-DC, Transmission & Distribution Handout
1. Indicate True or False:
_______DC requires information about frequency
_______DC travels in one direction only
_______DC’s intensity does not vary with time
_______DC is used for transmission through high tension wires
_______AC requires information about frequency
_______AC travels in one direction only
_______AC’s voltage does not vary with time
_______AC is used for transmission through high tension wires
_______DC is converted to AC using a rectifier
_______AC’s intensity can be changed using a transformer
_______AC’s voltage can be changed using a transformer
2. If the current intensity for an electrical tool that works with AC is measured to be 25A:
2.1
What are the values around which it (I) oscillates?
2.2
What is the value of Vrms and which are the values for Vpeak if it draws 4200 W?
3. A transformer lowers voltage from 120000V to 12000V. If the primary winding (input)
draws 1000A, what is the current intensity at the output (secondary winding) of the
transformer?
3.1
3.2
What type of transformer is this? ______________________________________
How do you expect the number of turns of the input to be compared to that of the
output? ___________________________________________________________
4. Choose the most appropriate answer
4.1
In a step down transformer, the voltage of the input is ____than that of the output
a- Lower
b- Higher
c-Equal
4.2
In a step down transformer, the current intensity at the output is ____than at the
input
a- Lower
b- Higher
c-Equal
4.3
In a step down transformer, the number of turns of the input is ____ than that of
the output
a- Lower
b- Higher
c-Equal
4.4
In a step down transformer, the Joule effect is ____ for the input
a- Lower
b- Higher
c-Equal
4.5
In a step up transformer, the voltage of the output is ____than that of the input
b- Lower
c- Higher
d-Equal
4.6
In a step up transformer, the current intensity at the input is ____than at the
output
b- Lower
c- Higher
d-Equal
4.7
In a step up transformer, the number of turns of the output is ____ than that of the
input
b- Lower
c- Higher
d-Equal
4.8
In a step up transformer, the Joule effect is ____ for the output
b- Lower
c- Higher
d-Equal
5. Indicate the correct diagram.
A
B
C
6. Indicate what type of branch circuit (120V or 240V) would you get if you connect:
6.1
6.2
6.3
A red live wire and and a white neutral wire: _______
A black live wire and and a white neutral wire: _______
A red live wire, a black live and and a white neutral wire: _______
7. Having three conductors of the following AWG size: 8, 12, 14, indicate
7.1
7.2
7.3
The biggest one (diameter): _____
The one with the lowest resistance: _____
The one that would carry the least amount of current due to Joule effect: _____
8. Why can devices connected with general purpose branch circuits can function if one of
them is burnt out?
9. Check out the situations that do NOT apply.
9.1
Multiple plugging of devices should be avoided in order to:
____Avoid excess of voltage in the line
____Avoid excess of heating due to Joule effect
____Avoid risk of electric fire
____Avoid excess of demanded current intensity
9.2
The third prong should never be removed because:
____It brings current to ground
____It keeps you from suffering an electroshock
____It is used for insulated housing appliances
10. Complete the 240V branch circuit below knowing that the acceptable value for current
intensity is 25A.
10.1
10.2
10.3
In your drawing indicate the destination for each point of the outlet (2nd diagram)
Indicate the points of the outlet to which a heating element is connected to (2nd
diagram)
Indicate the points of the outlet to which a motor is connected to (2nd diagram)