Q150 / 150 · MHT CET 2026 (18 April Shift 2) · Physics
In an NPN transistor, the collector current is 28 mA. If 80% electrons reach the collector, its base current in mA is
- Correct answerA$7$ mA
- B$14$ mA
- C$28$ mA
- D$35$ mA
Solution
Given $I_C = 28$ mA.
Since $80$ percent of the electrons emitted reach the collector, the collector current is given by:
$I_C = \dfrac{80}{100} I_E$
$28 = 0.8 I_E$
$I_E = \dfrac{28}{0.8} = 35$ mA
The relation between emitter, base, and collector currents is:
$I_E = I_B + I_C$
$I_B = I_E - I_C$
$I_B = 35 - 28 = 7$ mA
Answer: $7$ mA
Since $80$ percent of the electrons emitted reach the collector, the collector current is given by:
$I_C = \dfrac{80}{100} I_E$
$28 = 0.8 I_E$
$I_E = \dfrac{28}{0.8} = 35$ mA
The relation between emitter, base, and collector currents is:
$I_E = I_B + I_C$
$I_B = I_E - I_C$
$I_B = 35 - 28 = 7$ mA
Answer: $7$ mA
Hence, the correct answer is option: 'A'.