Tag: circuit components

Questions Related to circuit components

A light emitting diode (LED) has a voltage drop of 2 V across it and passes a current of 10 mA. When it operates with a 6 V battery through a limiting resistor R, the value of R is 

physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

  1. 200 $\Omega$

  2. 400 $\Omega$

  3. 40 $k\Omega$

  4. 4 $k\Omega$

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Correct Option: B
Explanation:

Light emitting diode is a forward biased P-N junction which emits light.

The voltage across it = 2 v

Battery voltage = 6 v

Hence total voltage in the circuit = V = 6 - 2 = 4 v

since a LED has 0 resistance in the forward biased region, total resistance in the circuit

= 0 + r = r

current I = 10 mA = 10/1000 A = 0.01 A

we know that,

R = V/I

=> r = 4/0.01 = 400Ω

Hence the value of the limiting resistor is 400Ω

When a diode is heavily doped the 

physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

  1. Zener voltage will be low

  2. Avalanche voltage will be high

  3. Depletion region will be thin

  4. Leakage current will be low

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Correct Option: A
Explanation:

The value of reverse voltage at which this occurs is controlled by the amount ot doping of the diode. A heavily doped diode has a low Zener breakdown voltage, while a lightly doped diode has a high Zener breakdown voltage. At voltages above approximately 8V, the predominant mechanism is the avalanche breakdown.

The relation between dynamic plate resistance $\left( r _ { p } \right)$ of a vacuum diode and plate current in the space charge limited region, is 

physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

  1. $r _ { p } \propto I _ { p }$

  2. $r _ { p } \propto I _ { p } ^ { 3 / 2 }$

  3. $r _ { p } \propto \frac { 1 } { I _ { p } }$

  4. $r _ { p } \propto \frac { 1 } { \left( I _ { p } \right) ^ { 1 / 3 } }$

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Correct Option: A

Zener diode is used as

physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

  1. Half wave rectifier

  2. Full wave rectifier

  3. ac voltage stabilizer

  4. dc voltage stabilizer

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Correct Option: A

What is the work function of tungsten at $1500\ K$ temperature, when a diode valve with a tungsten filament works at $1500\ K$? Assume the work function of tungsten at $0\ K$ is $4.52\ eV$:

physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

  1. $4.71\ eV$

  2. $0.39\ eV$

  3. $8.86\ eV$

  4. $1.25\ eV$

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Correct Option: A

Diodes are used to ___________.

physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

  1. convert DC into AC

  2. convert AC into DC

  3. resistance control

  4. current regulation

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Correct Option: B
Explanation:

Diodes are used as a rectifier. A rectifier is a device made from heavily doped p-n junction diode that is used to convert a.c to d.c.