Test: Series Circuits & Parallel Networks - Electrical Engineering (EE) MCQ

In a series circuit, the current across all elements remain the same and the total volt-age of the circuit is the sum of the voltages across all the elements.

• The 60 ohm resistance is shorted since current always chooses the low resistance path. So, whole of the current will flow through the alternative route and there will be 0 current through 60Ω resistance.
• As, Voltage across short circuit is equal to zero, hence voltage across the resistor is 0.

Total current = 150/(6+12+15) = 4.55A.

V across 6 ohm = Total current x resistance

= 4.55 * 6 = 27.24V.

Since the two bulbs are connected in series, if the first bulb burns out there is a break in the circuit and hence the second bulb does not glow.

V=IR hence voltage across a series resistor circuit is proportional to the value of the resistance because current remains same in series circuit.

In a series circuit, the current remains the same across all resistors hence the voltage divides proportionally among all resistors.

A short is just a wire. The potential difference between two points of a wire is zero hence the voltage measured is equal to zero.

Current is inversely proportional to resistance so resistance increased 2 times means current is decreased 2 times.

 In a parallel circuit, if one bulb blows out, it acts as an open circuit. Current does not flow in that branch but it continues to flow in the other branch hence the bulb continues to glow.

I = V/R. Since in parallel circuit, voltage is same across all resistors. Hence, across the 20 ohm resistor, V = 200V so I = 200/20  = 10A

 In parallel circuits, the current across the circuits vary whereas the voltage remains the same.

• The 1 ohm and 2-ohm resistor are in series which is in parallel to the 3-ohm resistor.
• The equivalent of these resistances is in series with the 4 ohms and 5-ohm resistor.
• Total R= 10.5 ohm. I=V/R= 120/10.5= 11.42A.

The voltage across all branches in a parallel circuit is the same as that of the source voltage. Hence the voltage across the 10 ohm resistor and the open circuit is the same=100V.

The voltage across a short is always equal to zero whether it is connected in series or parallel.

R=V/I. In this circuit I=5A and V=135V. Therefore, R=135/5=27 ohm.

The total current leaving a node is the same as the current that enters it. Total I=I₁+I₂+I₃=3+4+5=12A.

The resistors are connected in parallel, hence the equivalent resistance= 1/(1/20=1/20+1/20+1/20)=5ohm.

Batteries are generally connected in series so that we can obtain the desired voltage since voltages add up once they are connected in series.

 In series circuits the total resistance is the sum of all the resistance in the circuit, hence the total is greater than the largest resistance.

• All are In parallel so voltage is same
• I₁ =  ( R₂/R₁+R₂ )V = ( 3/8 )x5A = 1.875
• I2 = ( R₁/R₁+R₂ )V = ( 5/8 )x5A = 3.125

• 3 and 2 ohm resistors are in series, So 3+2 = 5ohm
• 5 and 5 ohm resistors are in parallel. So 5 || 5 = 2.5ohms
• 2.5 and1.5ohm resistors are in series. So 2.5+1.5 = 4ohms
• Finally, 4 and 4ohm resistors are in parallel. So 4 || 4 = 2ohms.
  That is resistance across A and B terminals is 2 ohms

Ideal Voltage Source: An ideal voltage source has zero internal resistance.

Practical Voltage Source: A practical voltage source consists of an ideal voltage source (V_S) in series with internal resistance (R_S).

An ideal voltage source and a practical voltage source can be represented as shown in the figure.

Ideal Current Source: An ideal voltage source has infinite resistance. Infinite resistance is equivalent to zero conductance. So, an ideal current source has zero conductance.

Practical Current Source: A practical current source is equivalent to an ideal current source in parallel with a high resistance or low conductance.

Ideal and practical current sources are represented as shown the below figure.

The circuit after removing the voltage source

The total resistance of the new circuit will be the equivalent resistance of the network.

R_eq = R_t = 3 + 2 + 2 = 7 Ω 

The equivalent resistance of the network is 7 Ω.

Resistances in parallel combination: When two or more resistances are connected across different branches such that the potential drop across them are the same, they are said to be in parallel connection.

The net resistance/equivalent resistance (R) of resistances in parallel is given by:
Equivalent resistance (R): 
EXPLANATION:
If n resistance connected in parallel the,

Hence,

Concept : 

Ideal current source: an ideal current source has infinite resistance. Infinite Resistance is equivalent to zero conductance. 

Practical current source: Practical current source is equivalent to the ideal current source in parallel with high resistance or low conductance.

Ideal and practical current sources are represented as given below :

Ideal current source: An ideal current source has infinite resistance. Infinite resistance is equivalent to zero conductance. So, an ideal current source has zero conductance.

Practical current source: A practical current source is equivalent to an ideal current source in parallel with high resistance or low conductance.

Ideal and practical current sources are represented as shown in the below figure:

Important Points

Ideal voltage source: An ideal voltage source have zero internal resistance.

Practical voltage source: A practical voltage source consists of an ideal voltage source (VS) in series with internal resistance (RS) as follows.

An ideal voltage source and a practical voltage source can be represented as shown in the figure.