~ (squiggly line): You might see a squiggly line next to or above a V or A on the front of your multimeter, in addition to metric prefixes. This stands for alternating current (AC).
As in DC circuits, the instantaneous electric power in an AC circuit is given by P=VI where V and I are the instantaneous voltage and current. the power becomes: Averaging this power over a complete cycle gives the average power.
Alternating Current Circuits or AC circuits are simply circuits powered by an Alternating Source, either current or voltage. An Alternating Voltage or Current is one in which the amount of either the voltage or the current alters about a distinct mean value and reverses direction periodically.
Root mean square or R.M.S. value of Alternating current is defined as that value of steady current, which would generate the same amount of heat in a given resistance is given time, as is done by A.C. current , when maintained across the same resistance for the same time.
Batteries and electronic devices like TVs, computers and DVD players use DC electricity - once an AC current enters a device, it's converted to DC. A typical battery supplies around 1.5 volts of DC.
Simultaneous Analog The general formula for calculating the current in a circuit is I = V/R, where I is current, V is voltage and R is resistance. This equation will provide the current in units of amperes, provided the voltage is in volts and the resistance is in ohms.
Unit of electric current: ampere (A)The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 ×10−19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆νCs.
Both AC and DC describe types of current flow in a circuit. In direct current (DC), the electric charge (current) only flows in one direction. Electric charge in alternating current (AC), on the other hand, changes direction periodically.
AC Voltage
Represented by capital V with a wavy line on top, the symbol stands for voltage. You have to move the dial to this symbol when you want to measure the voltage of the object. You should use it when you are measuring AC voltage.Multimeters measure resistance by injecting a small current into the circuit, and then measuring the voltage drop across those points in the circuit. The known current, and the resulting voltage drop are then used to calculate the resistance using Ohm's Law, V=I*R. Then probe the desired area of the circuit.
With a digital meter that auto-senses polarity, you will get a negative accurate reading if you have a DC setting and measure DC with the polarity reversed. It will show zero or an error if the polarity is reversed and it isn't auto-sensing. AC will display as zero voltage on a DC setting, regardless of the polarity.
Direct current (DC) is electrical current which flows consistently in one direction. The current that flows in a flashlight or another appliance running on batteries is direct current.
To determine the number of amps any one device pulls, you must know the wattage of the device, and the device's voltage.
- Determine the number of volts and watts required by each device to be added to the circuit.
- Divide the number of watts required by the volts to determine the needed amperage.
Calculating Amperage
A simple formula for calculating amps is to take the watts and divide that by the volts. So, for instance, if the wattage of the lighting fixture you're working with is 60 and the volts are 12, divide 60 by 12 and you will get five, which are the amps.
