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GRADE 8 PRACTICE

Physics Problems: Conductor connections, Grade 8

Series, parallel and mixed circuits.

18 problems across 3 sub-topics
Practise in the interactive mode

Here the conditions and analysis of the solution can be read without an account. In the simulator, you need to collect the same analyzes yourself: “Given,” formulas, order of steps and answer.

Problem statements

The answer options are there to check against, and the walkthrough opens under each problem.

18 problems
Position in this set: 1 from 18

Problem #49

Series connection

What concept does the description correspond to: “The elements are connected one after the other without branching, so the same current passes through them.»?

Answer options

  1. \text{Series connection}
  2. \text{Series circuit measurement}
  3. \text{A break in a series circuit}
  4. \text{Capillary action}
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Given
\text{Description}
\text{The elements are connected one after the other without branching, so the same current passes through them.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    The total voltage is distributed between the elements, and the equivalent resistance is equal to the sum of the resistances.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Series connection}

Answer\text{Concept} = \text{Series connection}

Position in this set: 2 from 18

Problem #50

Series connection

What concept does the description correspond to: “The ammeter shows the same current in different places, and the sum of the voltages across the elements is equal to the source voltage.»?

Answer options

  1. \text{Series circuit measurement}
  2. \text{Series connection}
  3. \text{A break in a series circuit}
  4. \text{Capillary action}
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Given
\text{Description}
\text{The ammeter shows the same current in different places, and the sum of the voltages across the elements is equal to the source voltage.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    Checking these relationships helps detect assembly errors and confirm connection rules.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Series circuit measurement}

Answer\text{Concept} = \text{Series circuit measurement}

Position in this set: 3 from 18

Problem #51

Conductor connections

4 ohm and 6 ohm resistors are connected in series and connected to 12 V. Find the total resistance and current.

Answer options

  1. 10\,\text{Ом};\ 1{,}2\,\text{А}
  2. 2{,}4\,\text{Ом};\ 5\,\text{А}
  3. 10\,\text{Ом};\ 120\,\text{А}
  4. 24\,\text{Ом};\ 0{,}5\,\text{А}
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Given
R_1
4\,\text{Ом}
R_2
6\,\text{Ом}
U
12\,\text{В}
Find

RI

  1. R=R_1+R_2R=4+6\,\text{Ом}R = 10\,\text{Ом}
  2. I=\frac{U}{R}I=\frac{12}{10}\,\text{А}I = 1{,}2\,\text{А}

Answer10\,\text{Ом}1{,}2\,\text{А}

Position in this set: 4 from 18

Problem #52

Parallel and mixed connection

What concept does the description correspond to: “The elements are connected to one pair of nodes, so the voltage on each branch is the same.»?

Answer options

  1. \text{Parallel connection}
  2. \text{Equivalent resistance}
  3. \text{Series-parallel circuit}
  4. \text{Capillary action}
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Given
\text{Description}
\text{The elements are connected to one pair of nodes, so the voltage on each branch is the same.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    The total current is equal to the sum of the branch currents, and adding a new branch reduces the equivalent resistance.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Parallel connection}

Answer\text{Concept} = \text{Parallel connection}

Position in this set: 5 from 18

Problem #53

Parallel and mixed connection

What concept does the description correspond to: “One resistance that, at the same voltage, draws the same total current as the entire combination.»?

Answer options

  1. \text{Equivalent resistance}
  2. \text{Parallel connection}
  3. \text{Series-parallel circuit}
  4. \text{Capillary action}
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Given
\text{Description}
\text{One resistance that, at the same voltage, draws the same total current as the entire combination.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    For parallel branches, the equivalent resistance is less than any individual resistance.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Equivalent resistance}

Answer\text{Concept} = \text{Equivalent resistance}

Position in this set: 6 from 18

Problem #54

Conductor connections

6 ohm and 3 ohm resistors are connected in parallel at 12 V. Find the equivalent resistance and the total current.

Answer options

  1. 2\,\text{Ом};\ 6\,\text{А}
  2. 9\,\text{Ом};\ 1{,}33\,\text{А}
  3. 2\,\text{Ом};\ 24\,\text{А}
  4. 18\,\text{Ом};\ 0{,}67\,\text{А}
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Given
R_1
6\,\text{Ом}
R_2
3\,\text{Ом}
U
12\,\text{В}
Find

RI

  1. R=\frac{R_1R_2}{R_1+R_2}R=\frac{6\cdot3}{6+3}\,\text{Ом}R = 2\,\text{Ом}
  2. I=\frac{U}{R}I=\frac{12}{2}\,\text{А}I = 6\,\text{А}

Answer2\,\text{Ом}6\,\text{А}

Position in this set: 7 from 18

Problem #169

Series connection

resistors 4 and 8 Ohm connected sequentially. Find Total resistance.

Answer options

  1. 12\,\text{Ом}
  2. 24\,\text{Ом}
  3. 6\,\text{Ом}
  4. 36\,\text{Ом}
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Given
R_1
4\,\text{Ом}
R_2
8\,\text{Ом}
Find

R

  1. R=R_1+R_2R=4 + 8R=12\,\text{Ом}

    In a series circuit, the resistances add up.

Answer12\,\text{Ом}

Position in this set: 8 from 18

Problem #170

Series connection

resistors 6 and 9 Ohm connected sequentially. Find Total resistance.

Answer options

  1. 30\,\text{Ом}
  2. 15\,\text{Ом}
  3. 7{,}5\,\text{Ом}
  4. 45\,\text{Ом}
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Given
R_1
6\,\text{Ом}
R_2
9\,\text{Ом}
Find

R

  1. R=R_1+R_2R=6 + 9R=15\,\text{Ом}

    In a series circuit, the resistances add up.

Answer15\,\text{Ом}

Position in this set: 9 from 18

Problem #171

Series connection

Consistently connected resistors 3 and 5 Ohm connected to voltage 16 B. Find current.

Answer options

  1. 4\,\text{А}
  2. 2\,\text{А}
  3. 1\,\text{А}
  4. 6\,\text{А}
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Given
R_1
3\,\text{Ом}
R_2
5\,\text{Ом}
U
16\,\text{В}
Find

I

  1. R=R_1+R_2R=3 + 5R=8\,\text{Ом}

    We find the total resistance.

  2. I=\frac{U}{R}I=\frac{16}{8}I=2\,\text{А}

    The same current passes through both resistors.

Answer2\,\text{А}

Position in this set: 10 from 18

Problem #172

Series connection

Consistently connected resistors 5 and 7 Ohm connected to voltage 36 B. Find current.

Answer options

  1. 6\,\text{А}
  2. 1{,}5\,\text{А}
  3. 3\,\text{А}
  4. 9\,\text{А}
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Given
R_1
5\,\text{Ом}
R_2
7\,\text{Ом}
U
36\,\text{В}
Find

I

  1. R=R_1+R_2R=5 + 7R=12\,\text{Ом}

    We find the total resistance.

  2. I=\frac{U}{R}I=\frac{36}{12}I=3\,\text{А}

    The same current passes through both resistors.

Answer3\,\text{А}

Position in this set: 11 from 18

Problem #173

Series connection

Two resistor 4 and 8 Ohm connected sequentially with source 18 B. Find Voltage across the second resistor.

Answer options

  1. 24\,\text{В}
  2. 6\,\text{В}
  3. 12\,\text{В}
  4. 36\,\text{В}
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Given
R_1
4\,\text{Ом}
R_2
8\,\text{Ом}
U
18\,\text{В}
Find

U_2

  1. R=R_1+R_2R=4 + 8R=12\,\text{Ом}

    Add up the resistances.

  2. I=\frac{U}{R}I=\frac{18}{12}I=1{,}5\,\text{А}

    Find the total current.

  3. U_2=IR_2U_2=1{,}5 \cdot 8U_2=12\,\text{В}

    Voltages are distributed proportionally to resistances.

Answer12\,\text{В}

Position in this set: 12 from 18

Problem #174

Series connection

Two resistor 5 and 15 Ohm connected sequentially with source 24 B. Find Voltage across the second resistor.

Answer options

  1. 36\,\text{В}
  2. 9\,\text{В}
  3. 54\,\text{В}
  4. 18\,\text{В}
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Given
R_1
5\,\text{Ом}
R_2
15\,\text{Ом}
U
24\,\text{В}
Find

U_2

  1. R=R_1+R_2R=5 + 15R=20\,\text{Ом}

    Add up the resistances.

  2. I=\frac{U}{R}I=\frac{24}{20}I=1{,}2\,\text{А}

    Find the total current.

  3. U_2=IR_2U_2=1{,}2 \cdot 15U_2=18\,\text{В}

    Voltages are distributed proportionally to resistances.

Answer18\,\text{В}

Position in this set: 13 from 18

Problem #175

Parallel and mixed connection

Currents flow in two parallel branches 2 and 3 A. Find the current in the unbranched part.

Answer options

  1. 10\,\text{А}
  2. 5\,\text{А}
  3. 2{,}5\,\text{А}
  4. 15\,\text{А}
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Given
I_1
2\,\text{А}
I_2
3\,\text{А}
Find

I

  1. I=I_1+I_2I=2 + 3I=5\,\text{А}

    Charge does not accumulate in the circuit node.

Answer5\,\text{А}

Position in this set: 14 from 18

Problem #176

Parallel and mixed connection

Currents flow in two parallel branches 3 and 5 A. Find the current in the unbranched part.

Answer options

  1. 16\,\text{А}
  2. 4\,\text{А}
  3. 8\,\text{А}
  4. 24\,\text{А}
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Given
I_1
3\,\text{А}
I_2
5\,\text{А}
Find

I

  1. I=I_1+I_2I=3 + 5I=8\,\text{А}

    Charge does not accumulate in the circuit node.

Answer8\,\text{А}

Position in this set: 15 from 18

Problem #177

Parallel and mixed connection

resistors 6 and 3 Ohms connected in parallel at voltage 12 B. Find the total current.

Answer options

  1. 12\,\text{А}
  2. 3\,\text{А}
  3. 6\,\text{А}
  4. 18\,\text{А}
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Given
R_1
6\,\text{Ом}
R_2
3\,\text{Ом}
U
12\,\text{В}
Find

I

  1. I_1=\frac{U}{R_1}I_1=\frac{12}{6}I_1=2\,\text{А}

    Both branches have the same voltage.

  2. I_2=\frac{U}{R_2}I_2=\frac{12}{3}I_2=4\,\text{А}

    Separately, we find the current of the second branch.

  3. I=I_1+I_2I=2 + 4I=6\,\text{А}

    We add up the branch currents.

Answer6\,\text{А}

Position in this set: 16 from 18

Problem #178

Parallel and mixed connection

resistors 8 and 4 Ohms connected in parallel at voltage 24 B. Find the total current.

Answer options

  1. 18\,\text{А}
  2. 4{,}5\,\text{А}
  3. 27\,\text{А}
  4. 9\,\text{А}
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Given
R_1
8\,\text{Ом}
R_2
4\,\text{Ом}
U
24\,\text{В}
Find

I

  1. I_1=\frac{U}{R_1}I_1=\frac{24}{8}I_1=3\,\text{А}

    Both branches have the same voltage.

  2. I_2=\frac{U}{R_2}I_2=\frac{24}{4}I_2=6\,\text{А}

    Separately, we find the current of the second branch.

  3. I=I_1+I_2I=3 + 6I=9\,\text{А}

    We add up the branch currents.

Answer9\,\text{А}

Position in this set: 17 from 18

Problem #179

Parallel and mixed connection

resistors 6 and 3 Ohms connected in parallel; there is a resistor in series with this pair 4 Ohm. Whole circuit voltage 18 B. Find the voltage across the parallel pair.

Answer options

  1. 12\,\text{В}
  2. 3\,\text{В}
  3. 18\,\text{В}
  4. 6\,\text{В}
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Given
R_1
6\,\text{Ом}
R_2
3\,\text{Ом}
R_3
4\,\text{Ом}
U
18\,\text{В}
Find

V

  1. R=\frac{R_1R_2}{R_1+R_2}R=\frac{6 \cdot 3}{(6 + 3)}R=2\,\text{Ом}

    We replace the parallel pair with an equivalent resistance.

  2. I=\frac{U}{R+R_3}I=\frac{18}{(2 + 4)}I=3\,\text{А}

    We find the current in the entire circuit.

  3. V=IRV=3 \cdot 2V=6\,\text{В}

    The voltage across the pair is equal to the current of the common circuit multiplied by its resistance.

Answer6\,\text{В}

Position in this set: 18 from 18

Problem #180

Parallel and mixed connection

resistors 12 and 6 Ohms connected in parallel; there is a resistor in series with this pair 2 Ohm. Whole circuit voltage 24 B. Find the voltage across the parallel pair.

Answer options

  1. 16\,\text{В}
  2. 32\,\text{В}
  3. 8\,\text{В}
  4. 48\,\text{В}
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Given
R_1
12\,\text{Ом}
R_2
6\,\text{Ом}
R_3
2\,\text{Ом}
U
24\,\text{В}
Find

V

  1. R=\frac{R_1R_2}{R_1+R_2}R=\frac{12 \cdot 6}{(12 + 6)}R=4\,\text{Ом}

    We replace the parallel pair with an equivalent resistance.

  2. I=\frac{U}{R+R_3}I=\frac{24}{(4 + 2)}I=4\,\text{А}

    We find the current in the entire circuit.

  3. V=IRV=4 \cdot 4V=16\,\text{В}

    The voltage across the pair is equal to the current of the common circuit multiplied by its resistance.

Answer16\,\text{В}

The theory behind these problems

Work through the topic if a problem will not give in.

Series connectionCurrent, voltage and equivalent resistance of a series circuit.Parallel and mixed connectionCurrent splitting, shared voltage and basic series-parallel circuits.

Formulas by topic

Look up symbols and units of measurement in the reference.

Electrical voltageU · ВElectric currentI · АElectrical resistanceR · Ом