A solenoid of length L L\,L has N N\,N turns of wire of resistance R R\,R wound around a core. When connected to a direct current (DC) power supply of constant potential difference V V\,V and negligible internal resistance, a magnetic field of flux density B B\,B is established at its centre.
The solenoid is replaced by a new solenoid with twice the length (2L) and twice the number of turns (2N) made from the same type of wire (with the same cross-sectional radius of the turns). This new solenoid is connected to the same power supply VVV.
What is the magnetic flux density at the centre of the new solenoid?
0.25B0.25 B0.25B
0.50B0.50 B0.50B
1.0B1.0 B1.0B
2.0B2.0 B2.0B