A dynamo is an electric generator made from coils of wires that are made to turn in a permanent magnetic field by way of a commutator. Essentially any electric DC motor with a permanent magnet can become a dynamo.

Kelly Frayne

A dynamo is an electrical generator that creates direct current using a commutator. It is basically a DC generator, i.e. an electrical machine which converts mechanical power into direct current electrical power.

Dynamos are divided into two general lands: direct current (D. C.) and alternating-current dynamos (A. C.) or simply alternators.

Transformers do not pass direct current (DC), and can be used to take the DC voltage (the constant voltage) out of a signal while keeping the part that changes (the AC voltage). In the electrical grid transformers are key to changing the voltages to reduce how much energy is lost in electrical transmission.

There is no such thing as a DC transformer. Transformers are electrical components designed to do one of three things: decouple one circuit from another, increase voltage from one value to a higher potential, or decrease voltage to a lower potential. Transformers operate on alternating current only.

Direct current(DC) has no time varying field because current is constant as well as there is no relatively motion between coil and core(magnetic circuit) of the transformer. Transformer fails to transfer power from primary to secondary. Thus DC supply is not used for transformer.

rectifier

Though both AC and DC currents and shock are lethal, more DC current is required to have the same effect as AC current. For example, if you are being electrocuted or shocked 0.5 to 1.5 milliamps of AC 60 Hz current is required and up to 4 mA of DC current is required.

Alternating current (A.C) is five times more dangerous than Direct current (D.C). The frequency of the alternating current is the main reason for this severe effect on the human body. The frequency of 60 cycles is in an extremely harmful range. At this frequency, even a small voltage of 25 volts can kill a person.

220 volt a.c. means the effecitve or virtual value of a.c. is 220 volt, i.e., Ev=220 volt. But 220 volt d.c. has the same peak value (i.e., 220 volt only). Moreover, the shock of a.c. is attractive and that of d.c. is repulsive. Hence 220 volt a.c. is more dangerous than 220 volt d.c.

For example, In case of AC, the safest limit is 50V (or 25V in humid) where in DC, the safe limit is 120V DC. Same is the case for current, i.e. lower currents are needed for the same effect on human body is compared to DC which is low.

The voltage and frequency of alternating current (AC) electricity used in homes varies from country to country throughout the world. Typically, either 110-volt AC (110V) or 220-volt AC (220V) is used. Most countries use 50Hz (50 Hertz or 50 cycles per second) as their AC frequency. Only a handful use 60Hz.

The major advantage that AC electricity has over DC electricity is that AC voltages can be readily transformed to higher or lower voltage levels, while it is difficult to do that with DC voltages. Since high voltages are more efficient for sending electricity great distances, AC electricity has an advantage over DC.

That is why portable electronics – flashlights, cell phones, laptops – use DC power; they have to store it. Because the electric grid provides AC, the electricity must get converted to DC when you want to charge a portable device.

DC power is significantly more energy efficient than AC power. DC motors and appliances have higher efficiency and power to size characteristics. DC-based lighting (LED) is as much as 75% more efficient than incandescent lighting.

Fans can run on both AC as well as DC according to the circuitry used inside it. But in recent years DC technology is being used to run residential and industrial ceiling fans. As our power sources are AC , so we have to convert a AC motor fan to DC to be able to use. DC fans consume 70% less power than the AC fans.

Which Motor Is More Powerful: AC or DC? AC motors are generally considered to be more powerful than DC motors because they can generate higher torque by using a more powerful current. However, DC motors are typically more efficient and make better use of their input energy.

alternating current

Small 120Vac (or 240Vac for Europe) fan motors are often just capacitor run AC motors or split phase AC motors. Really small AC fans use shaded pole motors. Now if you mean a computer fan, well, the answer is more complicated. They require DC voltage to run, but the motor itself is really a 3 phase AC motor.

Fan Types. A 2-wire fan has power and ground terminals. A 3-wire fan has power, ground, and a tachometric (“tach”) output, which provides a signal with frequency proportional to speed. A 4-wire fan has power, ground, a tach output, and a PWM-drive input.