Curriculum
- 25 Sections
- 92 Lessons
- 70 Hours
- 1.1 - Physical quantities and measurement techniques5
- 1.1Use of rulers and measuring cylinders to find a length or a volume
- 1.2Describe how to measure a variety of time intervals using clocks and digital timers
- 1.3Determine an average value for a small distance and for a short interval of time by measuring multiples (including the period of oscillation of a pendulum)
- 1.4Quiz Test 1Copy10 Minutes2 Questions
- 1.5TestCopy
- 1.2 - Motion4
- 1.3 - Mass and weight1
- 1.4 - Density1
- 1.5 - Forces5
- 1.6 - Momentum1
- 1.7 - Energy, work and power5
- 1.8 - Pressure1
- 2.1 - Kinetic particle model of matter5
- 2.2 - Thermal properties and temperature5
- 2.3 - Transfer of thermal energy5
- 3.1 - General properties of waves6
- 3.2 - Light7
- 3.3 - Electromagnetic spectrum2
- 3.4 - Sound3
- 4.1 - Simple phenomenon of magnetism3
- 4.2 - Electrical quantities5
- 4.3 - Electric circuits7
- 18.1Circuit diagram – Circuit components and their functionsCopy
- 18.2Effective or equivalent resistance in series and parallel circuitsCopy
- 18.3Behaviour of series and parallel circuitsCopy
- 18.4Function of LDR (Light Dependent Resistor) and thermistorCopy
- 18.5Potential divider and potentiometerCopy
- 18.6Use of relay in a circuitCopy
- 18.7Diode in half and full wave rectifier bridgeCopy
- 4.4 - Electrical safety2
- 4.5 - Electromagnetic effects6
- 5.1 - The nuclear model of the atom2
- 5.2 - Radioactivity5
- 6.1 - Earth and the Solar System2
- 6.2 - Stars and the Universe3
- Paper 6 instructions3
D.C. MotorCopy
Learning Objectives
- State that a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by:
–– increasing the number of turns on the coil
–– increasing the current
–– increasing the strength of the magnetic field - Relate this turning effect to the action of an electric motor including the action of a split-ring commutator
Contents to learn
D.C Motor
Electric motor is a device used to convert electrical energy into mechanical energy.
Its working principle is that when a current carrying conductors is placed in magnetic field , it experiences force.
The direction of force on this current carrying conductor can be determined by using Fleming’s Left Hand Rule.
Feming’s Left Hand Rule:
The objective of this rule is to determine the direction of force, on a current carrying conductor, when it is kept inside the magnetic field. If forefinger, middle finger and thumb are stretched perpendicular to each other such that forefinger points in the direction of applied magnetic field and middle finger points in the direction of electric current then thumb will point in the direction of force on a conductor.
An electric motor consists of a rectangular coil of many turns. This coil is called armature. It is fixed about an axis which is parallel to pendicular to its axis of rotation.
Ends of the coil are connected to two semi circular split rings. This ring is called commutator. A battery is connected to two carbon brushes to provide contact with each part of the commutator separately. When current passes through armature, forces act on its opposite sides in opposite direction. These forces make a couple of forces (torque) which rotate the armature about the fixed axis.
During rotation both parts of the commutator remain in contact with the carbon brushes separately. After rotation of 180o, the positions of the commutator is interchanged which reverse the dirction of the current through the armature and so the torque acts in the same direction (clockwise or anti-clockwise direction) .
Any object or parts of a device attached to the axle of motor will rotate along with it.
Note: If you need to show the diagram of D.C. Motor in the examination, then the below is one of the easy diagram to draw.
