A 2-page table summary that describes the key differences between motors and generators that you would need to know for the electrodynamics section according to the SAGS document. It explains the different uses, energy conversions, basic principles of operation, Fleming's Left Hand and Right Hand ...
Motors Generators
DC (direct) AC (alternating)
Uses Small appliances, computers, fans Electricity generation of power stations, generators at hospitals etc.
Energy Conversion Electrical energy Mechanical Energy Mechanical Energy Electrical Energy
What does it use? (Without a split ring Uses split ring commutator- two conducting halves that don’t Uses slip ring commutator: The current is reversed every half turn.
commutator, the motor will not rotate touch each other: It allows the current in the coil to alternate
continuously and will get stuck in the ( reverses/changes the direction of the current in the In an AC generator the brushes slide over slip rings that cause
vertical position.) armature) with every half turn (180), which allows the coil to constant contact between the rotating coil and the external circuit.
continue to rotate in the same direction. Constant rotation. The external circuit is therefore connected to the same side of the
Connects the conductor to the external circuit. coil. The result is that the direction of current changes with every
half rotation (cycle) of the coil. The current that is produced is
When coil is in vertical position- At 90, the split ring loses alternating current.
connection with the brushes and the battery. At this point
current stops flowing. Momentum (inertia) carries the coil
over until the brushes make contact with the split ring
commutator again. (180) Current direction is then changed.
Basic Principles of operation Battery used as a power source. It consists of a current An alternating current generator consists of a coil that is connected
carrying armature, connected to a source by a commutator to an external circuit by 2 slip rings which are connected to the
and brushes and placed in a magnetic field. When a current conductor. A coil is mechanically rotated in a magnetic field. When a
flows through the armature (coil windings) in a magnetic coil is mechanically rotated through a magnetic field, there is a
field, it will experience a turning force (torque). However, the change in flux. (A change in connection of the magnetic field and the
coil can only rotate continually in one direction if the conductor) According to Faraday’s Law, if there is a change in flux, an
direction of the current is reversed for each half turn of the emf will be induced in the coil which induces a current to flow if the
coil. This keeps the direction of the turning force on the circuit is closed.
armature constant.
Why a current-carrying coil placed in a Motor Effect: When the magnetic field around a current-
magnetic field will turn by referring to the carrying conductor interacts with another magnetic field, the
forces exerted on the sides of the coil conductor will experience a force.
perpendicular to the field. When a charge moves in a magnetic field it experiences a
force. The force experienced on both sides of the armature
creates torque which makes it (the coil) turn and rotate.
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