THE 



DIBECT-CUBBENT MOTOB 



CHAPTER I 



THE INDUCTION FACTOR 



\\ IIHN a straight conductor carrying a current is placed 

 in a uniform magnetic field in a plane at right angles to 

 the magnetic lines, it experiences a force urging it to 

 move in that plane at right angles to its own length. 



If H is the intensity of the field in lines per square 

 centimetre, /the length of the conductor in centimetres, 

 and i the, current in the conductor measured in amperes, 

 the force on the conductor is given by 



/W//HO-' dynes (1). 



The sign of/ can be changed by reversing the sign of 

 fit her // or i; hence the direction of the force can be 

 reversed by altering the sign of the field or of the current. 

 It' both are altered at the same time, the direction of th> 

 force is unchanged. 



