Physics

Current Electricity and Circuits

450 Questions

Current electricity and circuits questions cover resistors, EMF, internal resistance, and power calculations in series and parallel configurations. Solving these builds a strong understanding of electrical principles and circuit analysis. These physics problems are highly relevant for technical and science aptitude tests.

Resistor combinationsPower dissipationEMF and internal resistanceAC circuit analysisOperational amplifiers

Current Electricity and Circuits Questions

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

The current gain $\beta$-may be defined as

  1. the ratio of change in collector current to the change in emitter current for a constant collector voltage in a common base arrangement

  2. the ratio of change in collector current to the change in base current at constant collector voltage in a common emitter circuit

  3. the ratio of change in emitter current to the change in base current for constant emitter voltage in common emitter circuit

  4. the ratio of change in base current to the change in collector current in constant collector voltage in common emitter circuit
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

By definition, current gain  $\beta$ is defined as the ratio of change in collector current to change in base current for a constant collector voltage in a common emitter circuit.

$\beta =  \dfrac{\Delta i _C}{\Delta i _B}$   or simply    $\beta = \dfrac{I _C}{I _B}$
Generally,  $\beta$ has value between  $20$ and  $200.$

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

The current gain for a transistor working as common base amplifier is $0.96$. lf the emitter current is $7.2 mA$, the base current will be :

  1. $0.42 mA$
  2. $0.49 mA$
  3. $0.29 mA$
  4. $0.35 mA$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Here, $\displaystyle \alpha =0.96,{ I } _{ e }=7.2mA$
$\displaystyle \frac { { I } _{ c } }{ { I } _{ e } } =0.96$
$\displaystyle { I } _{ c }={ I } _{ e }\times 0.96=7.2\times 0.96=6.912mA$
Now,
$\displaystyle { I } _{ b }={ I } _{ c }-{ I } _{ c }=.2-6.912=0.29mA$

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

For a common emitter circuit if $I _C$ / $I _E$ =0.98 then current gain for common emitter circuit will be

  1. 4.9

  2. 98

  3. 49

  4. 9.8
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given that $\frac{I _{c}}{I _{e}}=0.98$

$\Rightarrow I _{c}=0.98I _{e}$
So we get $I _{b}=I _{e}-I _{c}=0.02I _{e}$
Therefore the current gain is $\frac{I _{c}}{I _{b}}=\frac{0.98}{0.02}=49$
Therefore the correct option is $C$.

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

In a p-n-p transistor, working as a common base amplifier, current gain is 0.96 and emitter current is 7.2mA. The base current is

  1. 0.20 mA

  2. 0.36 mA

  3. 0.29 mA

  4. 0.45 mA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Current gain $=\dfrac{I _{C}}{I _{B}}$
$I _{C}$ = collector current
$I _{B}$ = base current
So, $I _{B}=\dfrac{I _{C}}{current\, gain}= \dfrac{7.2\, mA}{0.96}=7.5\, mA$
As $I _{E}=I _{B}+I _{C}$
So, $I _{B}=I _{E}-I _{C}$
$=(7.5-7.2)\, mA=0.3\, mA$
$\approx 0.29\,mA$

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

A transistor is operated in common emitter configuration at $V _c=2V$ such that a change in the base current from $100\mu A$ to $300\mu A$ produces a change in the collector current from 10mA to 20mA. The current gain is

  1. $50$
  2. $75$
  3. $100$
  4. $25$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The base current changes from $100\mu A$ to $300 \mu A$ and produces a change in the collector current from $10mA$ to $20mA$

The change in collector current is $10mA$
The change in base current is $200\mu A$
The current gain is $\frac{10000}{200}=50$
Therefore option $C$ is correct.

Multiple choice physics electrical conductivity of liquids does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

Which of the following devices can be used to detect a weak current?

  1. Use of electric bulb in tester.

  2. Use of LED in tester.

  3. A tester using magnetic effects of current.

  4. Both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

LED glows even when a weak electric current flows through it. Also, even if the current is small, the deflection of the magnetic needle can be seen. Hence, tester using LED and magnetic effects of current can be used to detect a weak current.

Multiple choice physics electrical conductivity of liquids does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

Which of the following might be the reason that the current in the circuit is weak?

  1. Circuit of the tester might not be complete.

  2. The material may not be able to conduct electricity as easily as metals.

  3. The circuit of the tester is complete but still the bulb does not glow.

  4. Both A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Though a material may conduct electricity, it may not conduct it as easily as a metal. As a result, the circuit of the tester may be complete and yet the current through it may be too weak to make the bulb glow.

Multiple choice physics electrical conductivity of liquids does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

What happens when the current passing through the circuit is too weak?

  1. The filament does not get heated sufficiently and the bulb does not glow.

  2. The filament gets heated but the bulb does not glow.

  3. The filament does not get heated but the bulb glows.

  4. The filament gets heated and the bulb glows.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When the current through the circuit is too weak, the filament does not get heated sufficiently and the bulb does not glow.

Multiple choice physics electrical conductivity of liquids does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

Which of the following statement(s) is correct while conducting electricity through vegetable oil?

  1. The liquid (vegetable oil) allows the electric current to pass through. Since, it is a good conductor of electricity.

  2. The circuit of the tester is complete but the bulb does not glow.

  3. The circuit of the tester is not complete and hence the bulb does not glow.

  4. Both A and B
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the liquid (vegetable oil) does not allow the electric current to pass, the circuit of the tester is not complete and the bulb does not glow.

Multiple choice physics electrical conductivity of liquids does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

When electric current passes through the filaments of a bulb, it starts emitting light due to :

  1. heating effect of electric current.

  2. magnetic effect of electric current.

  3. chemical effect of electric current.

  4. lighting effect of electric current.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When electric current passes through the filaments of bulb, it starts emitting light due to heating effect of electric current.

Multiple choice physics electric circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

Which of the following is not a safety measure commonly used in electric circuits.

  1. An electric fuse is connected in parallel

  2. Proper earthing of all electric circuit is done

  3. Fuse protects the circuit from overloading

  4. All
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An electric fuse is connected in parallel. This is not a safety measure. Fuse is always connected in series.

Multiple choice physics electric circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

In domestic electrical circuit, switches are used in

  1. Neutral wire

  2. Earth wire

  3. Live wire

  4. All of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Switches are connected in live wire so that when the switch is in off position, no current flows through circuit. As a result there will not be any danger of electrical shock.

Multiple choice types of cells electricity physics

Which one of the following primary cells has e.m.f. $1.08  V$ and which remains fairly constant ?

  1. Daniel cell

  2. Simple voltaic cell

  3. Leclanche cell

  4. Dry cell
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

the Daniel cell is a type of electrochemical cell invented in 1836. it is consisted of a copper pot filled with a copper sulfate solution , in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode. Daniel cell is also called Zn-Cu cell and has constant e.m.f of 1.08 volts.