# Generators produce DC voltage

## Physics compact, basic knowledge 7, textbook

74 Supply with electrical energy 16 By increasing the number of loops (number of turns of the coil) the voltage that can be generated with the generator can be increased accordingly. If a consumer is connected to the ends of the coil with the help of slip rings, current can flow. The strength of the current depends on the size of the induced voltage and the size of the resistance of the consumer and induction coil in the generator. If a current of strength i flows through a generator at a voltage u, then the generator produces the total output u · i. Where does this service come from? Since the induction coil rotates in a magnetic field, a braking Lorentz force acts on the induction coil through which it flows. In order to maintain the rotation of the coil, mechanical work must be carried out continuously against the Lorentz force. With an ideal generator, this mechanical work is completely converted into electrical energy. Real generators achieve efficiencies of around 95%. DC generator and motor (D.C. generator and motor) When the conductor loop or the coil rotates in the magnetic field, the direction of the current changes after every half turn (alternating current). In order to generate direct current with a generator, the change in the direction of the current must be prevented after every half revolution. This is achieved with a so-called commutator (commutator, collector). 16.1.2 A major difference between AC and DC generators is the type of voltage tap. A commutator (commutator, collector) is used in the DC generator. In the simplest case, the commutator consists of two conductive half-cylinders with two insulating gaps between them. Each half cylinder is connected to one end of the coil. The insulating gaps run past the brushes at the moment when the polarity of the current direction in the conductor loop is reversed. This arrangement has the effect that one brush becomes the positive pole of the generator and the other brush becomes the negative pole. With such a direct current generator you can generate a current that changes its amount, but always flows in the same direction. A so-called pulsating direct current is generated with direct current generators. A1 Experiment: DC motors essentially have the same structure as DC generators. Voltage is applied to a DC motor. Investigate how the DC motor adapts to different loads! SN 0 B  Fig. 74.1 Direct current generator Fig. 74.2 Alternating current and pulsating direct current Voltage u Voltage u 0 0 U m U m Maximum voltage Maximum voltage Alternating voltage Pulsating direct voltage Angle of rotation t ω π 2 π Angle of rotation t ω π 2 π Fig. 74.3 DC motor For testing purposes only - property of the publisher öbv