1. DC Motor & DC Generator DC Machines Lab # 2 Arsalan A Rahim
Abdur Rehman Kashif

2. Magnetic Field of Current
The magnetic field lines around a long wire which carries an electric current form concentric circles around the wire. The direction of the magnetic field is perpendicular to the wire and is in the direction the fingers of your right hand would curl if you wrapped them around the wire with your thumb in the direction of the current.
Arsalan A Rahim
Abdur Rehman Kashif

3. DC Motor
Arsalan A Rahim
Abdur Rehman Kashif

4. Magnetic Interactions with Moving Charge
Arsalan A Rahim
Abdur Rehman Kashif

5. Magnetic Force on Moving Charge
Arsalan A Rahim
Abdur Rehman Kashif

6. Magnetic Force on a Current
Arsalan A Rahim
Abdur Rehman Kashif

7. Fleming’s Left Hand Rule
Fleming's left hand rule (for electric motors) shows the direction of the thrust on a conductor carrying a current in a magnetic field.
Arsalan A Rahim
Abdur Rehman Kashif

8. Magnetic Force The characteristics of this equation are as follows
1. The force is perpendicular to both the velocity v of the charge q and the magnetic field B.
2. The magnitude of the force is F = qvB sinθ where θ is the angle < 180 degrees between the velocity and the magnetic field. This implies that the magnetic force on a stationary charge or a charge moving parallel to the magnetic field is zero.
3. The direction of the force is given by the right hand rule. The force relationship above is in the form of a vector product.
Arsalan A Rahim
Abdur Rehman Kashif

9. Units of Magnetic Field, B
From the force relationship above it can be deduced that the units of magnetic field are
Newton seconds /(Coulomb meter) or
Newton per Ampere meter.
This unit is named the Tesla. It is a large unit, and the smaller unit Gauss is used for small fields like the Earth's magnetic field.
1 Tesla = 10,000 Gauss
The Earth's magnetic field is of the order of half a Gauss
Arsalan A Rahim
Abdur Rehman Kashif

10. Lorentz Force Law
The electric force is straightforward, being in the direction of the electric field if the charge q is positive,
The direction of the magnetic part of the force is given by the right hand rule.
Arsalan A Rahim
Abdur Rehman Kashif

11. Magnetic Field in DC Motor
Arsalan A Rahim
Abdur Rehman Kashif

12. Current in DC Motor
Arsalan A Rahim
Abdur Rehman Kashif

13. Motor Working
Arsalan A Rahim
Abdur Rehman Kashif

14. Force in DC Motor
Arsalan A Rahim
Abdur Rehman Kashif

15. DC Motor Operation
Arsalan A Rahim
Abdur Rehman Kashif

16. Commutator and Brushes on DC Motor
To keep the torque on a DC motor from reversing every time the coil moves through the plane perpendicular to the magnetic field, a split-ring device called a commutator is used to reverse the current at that point. The electrical contacts to the rotating ring are called “carbon brushes"
Arsalan A Rahim
Abdur Rehman Kashif

17. DC Generator
DC Generator work on the same principle as that of the DC Motor but in the reverse direction, i.e. the prime mover is attached to the Shaft, thus the voltage generated is available at the commutator.
Fleming’s Right Hand Rule is used to find out the direction of the current in the moving conductor placed in a magnetic field
Arsalan A Rahim
Abdur Rehman Kashif

18. Fleming's Right Hand Rule
Fleming's right hand rule (for generators) shows the direction of induced current flow when a conductor moves in a magnetic field.
Arsalan A Rahim
Abdur Rehman Kashif

19. Voltage Generated in a Moving Wire
Arsalan A Rahim
Abdur Rehman Kashif