Base Drive Is a Current Contract

Larger Base Resistor Weakens Drive

Changing only the base resistor changes the base current. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Four ohms gives one ampere for the same four-volt excess

With a 4 ohm base resistor, the base drive is 1 A.

IB=4 V4 Ω=1 AI_B={4\ \text{V}\over 4\ \Omega}=1\ \text{A}
Four-ohm base resistorThe base-current vector reaches one ampere.input 5 Vdrop 1 Vbase 1 A

Eight ohms halves the base current

Changing only the resistor to 8 ohm makes the base current 1/2 A.

IB=4 V8 Ω=12 AI_B={4\ \text{V}\over 8\ \Omega}={1\over 2}\ \text{A}
Eight-ohm base resistorSame voltage contract, smaller checked current.input 5 Vdrop 1 Vbase 1/2 A