Alternating Current (multiple CHoice)

There is no mention of a frequency, starting phase, or a period. It's impossible to answer this question without that information.In summary, the question asks for the time it takes for an alternating voltage of 30V given by v = 30sin(314t) to reach 30V for the first time. By finding the time at which the voltage reaches its first peak, it is determined that it takes approximately 5ms for the voltage to reach 30V. The question is incorrect as it does not provide enough information such as frequency, starting phase, or period.
  • #1
BSElectrician
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Homework Statement


An alternating voltage is given by [tex]v = 30\sin(314t)[/tex].The time taken by the voltage to reach 30V for the first time is:
A. 0.02s
B. 0.03s
C. 0.1s
D. 0.015s

Homework Equations


google for equation for instantaneaous current and voltage

The Attempt at a Solution


30 = 30sin(314t)
1 = sin(314t)
pi/2 = 314t
t = 0.005s
not in the choices

EDIT
30 = 30sin(314t - pi)
pi/2 = (314t - pi)
t = 0.015 from the choices

why do i need to subtract 180 degrees inside the sine eqn instead of adding
( Formula for n repeating cycles is v(t + nT) )
 
Last edited:
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  • #2
It would appear that the question is incorrect. Starting from time t = 0, the first positive peak occurs at approximately 5ms (milliseconds), which is what you first calculated.

By the way, is that the complete statement of the question in its original form?
 

1. What is Alternating Current (AC)?

Alternating Current, or AC, is a type of electrical current that reverses direction periodically. It is commonly used to power electrical devices in homes and businesses.

2. How is AC different from Direct Current (DC)?

The main difference between AC and DC is the direction of the current flow. While AC alternates direction, DC flows in only one direction. AC is also able to travel longer distances and can be easily converted to different voltages, making it more suitable for long-distance power transmission.

3. What are the advantages of using AC over DC?

AC has several advantages over DC, including the ability to be easily converted to different voltages, the ability to travel long distances without significant power loss, and the ability to power multiple devices simultaneously.

4. How is AC generated?

AC is typically generated using a device called an alternator, which converts mechanical energy (such as from a turbine) into electrical energy. The alternator produces a rotating magnetic field that induces an alternating current in a set of stationary coils.

5. What are the potential dangers of working with AC?

One of the main dangers of working with AC is the risk of electric shock. AC can also cause serious injuries or even death if not handled properly. It is important to always follow safety protocols and use proper protective equipment when working with AC.

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