If current is flowing through the base, Vbe is always about 0.7 Volt. The Ib becomes (V -Vbe)/Rb. In this circuit, Ib equal (5 - 0.7)/1000=4.3mA.
V ... The supply voltage to base
Vbe ... The voltage from emitter to base.
Ib ... The current into base
Rb ... The resister connected base.
