If a long hollow copper pipe carries a direct current, the magnetic field associated with the current will be :
Inside the pipe current enclosed will be zero so magnetic field will also be zero. Outside the pipe there will be net Magnetic field
In a co-axial straight cable, the central conductor and the outer conductor have equal currents in opposite directions. The magnetic induction is zero :
As outside the conductor net current enclosed is zero. using ampere circuital law Magnetic field is also zero.
A solenoid consists of 100 turns of wire and has a length of 10.0cm. The magnetic field inside the solenoid when it carries a current of 0.500 A will be :
\[ B= \mu_{0}ni \] where n is number of turns per unit length
n= 100/0.1=1000
i=0.5
substituting we get \[ B = 6.28\times 10^{-4} T\]
For the hollow thin cylindrical current carrying straight pipe which statement is correct:
Inside the hollow pipe, the magnetic field is zero according to Ampere's law. Since a current-carrying pipe is electrically neutral, the electric field outside the pipe is zero.