fizikzauglom

GRADE 8 PRACTICE

Physics Problems: Electric current, Grade 8

Sources, circuits, current and voltage.

18 problems across 4 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 #37

Electric current and circuit

What concept does the description correspond to: “Ordered motion of charged particles, requiring mobile carriers and an electric field.»?

Answer options

  1. \text{Electric current}
  2. \text{Electrical source}
  3. \text{Effects of electric current}
  4. \text{Capillary action}
Show the walkthroughHide the walkthrough
Given
\text{Description}
\text{Ordered motion of charged particles, requiring mobile carriers and an electric field.}
Find

\text{name concepts}

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

    In metals, carriers are electrons; conventional current direction is opposite to their directed motion.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Electric current}

Answer\text{Concept} = \text{Electric current}

Position in this set: 2 from 18

Problem #38

Electric current and circuit

What concept does the description correspond to: “A device that separates charges by converting chemical, mechanical, light or other energy.»?

Answer options

  1. \text{Electrical source}
  2. \text{Electric current}
  3. \text{Effects of electric current}
  4. \text{Capillary action}
Show the walkthroughHide the walkthrough
Given
\text{Description}
\text{A device that separates charges by converting chemical, mechanical, light or other energy.}
Find

\text{name concepts}

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

    The source maintains a potential difference, and the closed circuit provides a charge path. Read its diagram using standard component symbols.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Electrical source}

Answer\text{Concept} = \text{Electrical source}

Position in this set: 3 from 18

Problem #39

Electric current

There are free electrons in a metal wire. What additional condition is necessary for a stable current?

Answer options

  1. \text{Electric field B closed chains}
  2. \text{Complete absence resistance}
  3. \text{Mandatory Heating wires}
  4. \text{Immobility everyone electrons}
Show the walkthroughHide the walkthrough
Given
\text{carriers}
\text{free electrons}
Find

\text{second condition current}

  1. \text{free carriers without fields moving chaotically}
  2. \text{Field creates directed component movement}\text{needed field and closed chain}

Answer\text{electric field B closed chains}

Position in this set: 4 from 18

Problem #40

Current, voltage and measuring instruments

What concept does the description correspond to: “A physical quantity equal to the charge passing through the cross section of a conductor per unit time.»?

Answer options

  1. \text{Electric current}
  2. \text{Electrical voltage}
  3. \text{Connecting measuring instruments}
  4. \text{Capillary action}
Show the walkthroughHide the walkthrough
Given
\text{Description}
\text{A physical quantity equal to the charge passing through the cross section of a conductor per unit time.}
Find

\text{name concepts}

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

    The ammeter is connected in series so that the same current passes through it as through the element under study.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Electric current}

Answer\text{Concept} = \text{Electric current}

Position in this set: 5 from 18

Problem #41

Current, voltage and measuring instruments

What concept does the description correspond to: “A physical quantity equal to the work done by an electric field to transfer a unit charge.»?

Answer options

  1. \text{Electrical voltage}
  2. \text{Electric current}
  3. \text{Connecting measuring instruments}
  4. \text{Capillary action}
Show the walkthroughHide the walkthrough
Given
\text{Description}
\text{A physical quantity equal to the work done by an electric field to transfer a unit charge.}
Find

\text{name concepts}

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

    A voltmeter is connected in parallel across a section because it compares the electrical states at its two ends.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Electrical voltage}

Answer\text{Concept} = \text{Electrical voltage}

Position in this set: 6 from 18

Problem #42

Electric current

120 C of charge passed through the cross section of the conductor in 60 s. Find the current.

Answer options

  1. 2\,\text{А}
  2. 0{,}5\,\text{А}
  3. 60\,\text{А}
  4. 7200\,\text{А}
Show the walkthroughHide the walkthrough
Given
q
120\,\text{Кл}
t
60\,\text{с}
Find

I

  1. I=\frac{q}{t}I=\frac{120}{60}\,\text{А}I = 2\,\text{А}

Answer2\,\text{А}

Position in this set: 7 from 18

Problem #145

Electric current and circuit

Via transverse section conductor for 20 s charge passed 60 class Find force current.

Answer options

  1. 3\,\text{А}
  2. 6\,\text{А}
  3. 1{,}5\,\text{А}
  4. 9\,\text{А}
Show the walkthroughHide the walkthrough
Given
t
20\,\text{с}
q
60\,\text{Кл}
Find

I

  1. I=\frac{q}{t}I=\frac{60}{20}I=3\,\text{А}

    Current shows the charge passed per unit of time.

Answer3\,\text{А}

Position in this set: 8 from 18

Problem #146

Electric current and circuit

Via transverse section conductor for 30 s charge passed 120 class Find force current.

Answer options

  1. 8\,\text{А}
  2. 4\,\text{А}
  3. 2\,\text{А}
  4. 12\,\text{А}
Show the walkthroughHide the walkthrough
Given
t
30\,\text{с}
q
120\,\text{Кл}
Find

I

  1. I=\frac{q}{t}I=\frac{120}{30}I=4\,\text{А}

    Current shows the charge passed per unit of time.

Answer4\,\text{А}

Position in this set: 9 from 18

Problem #147

Electric current and circuit

Electric current 0{,}5 A constant B current 4 min. Which charge passed by chains?

Answer options

  1. 240\,\text{Кл}
  2. 120\,\text{Кл}
  3. 60\,\text{Кл}
  4. 360\,\text{Кл}
Show the walkthroughHide the walkthrough
Given
I
0{,}5\,\text{А}
t
4\,\text{мин}
Find

q

  1. T=60tT=4 \cdot 60T=240\,\text{с}

    Convert minutes to seconds.

  2. q=ITq=0{,}5 \cdot 240q=120\,\text{Кл}

    With constant current, charge is proportional to time.

Answer120\,\text{Кл}

Position in this set: 10 from 18

Problem #148

Electric current and circuit

Electric current 0{,}8 A constant B current 5 min. Which charge passed by chains?

Answer options

  1. 480\,\text{Кл}
  2. 120\,\text{Кл}
  3. 240\,\text{Кл}
  4. 720\,\text{Кл}
Show the walkthroughHide the walkthrough
Given
I
0{,}8\,\text{А}
t
5\,\text{мин}
Find

q

  1. T=60tT=5 \cdot 60T=300\,\text{с}

    Convert minutes to seconds.

  2. q=ITq=0{,}8 \cdot 300q=240\,\text{Кл}

    With constant current, charge is proportional to time.

Answer240\,\text{Кл}

Position in this set: 11 from 18

Problem #149

Electric current and circuit

B first 20 with by chains passed current 2 A, then B current 40 with current 5 A. Find average force current for everything time.

Answer options

  1. 8\,\text{А}
  2. 2\,\text{А}
  3. 4\,\text{А}
  4. 12\,\text{А}
Show the walkthroughHide the walkthrough
Given
t_1
20\,\text{с}
I_1
2\,\text{А}
t_2
40\,\text{с}
I_2
5\,\text{А}
Find

I_{\text{ср}}

  1. q_1=I_1t_1q_1=2 \cdot 20q_1=40\,\text{Кл}

    Find the charge of the first gap.

  2. q_2=I_2t_2q_2=5 \cdot 40q_2=200\,\text{Кл}

    Find the charge of the second gap.

  3. I_{\text{ср}}=\frac{q_1+q_2}{t_1+t_2}I_{\text{ср}}=\frac{(40 + 200)}{(20 + 40)}I_{\text{ср}}=4\,\text{А}

    We divide the entire charge for the entire time.

Answer4\,\text{А}

Position in this set: 12 from 18

Problem #150

Electric current and circuit

B first 30 with by chains passed current 3 A, then B current 30 with current 7 A. Find average force current for everything time.

Answer options

  1. 10\,\text{А}
  2. 2{,}5\,\text{А}
  3. 15\,\text{А}
  4. 5\,\text{А}
Show the walkthroughHide the walkthrough
Given
t_1
30\,\text{с}
I_1
3\,\text{А}
t_2
30\,\text{с}
I_2
7\,\text{А}
Find

I_{\text{ср}}

  1. q_1=I_1t_1q_1=3 \cdot 30q_1=90\,\text{Кл}

    Find the charge of the first gap.

  2. q_2=I_2t_2q_2=7 \cdot 30q_2=210\,\text{Кл}

    Find the charge of the second gap.

  3. I_{\text{ср}}=\frac{q_1+q_2}{t_1+t_2}I_{\text{ср}}=\frac{(90 + 210)}{(30 + 30)}I_{\text{ср}}=5\,\text{А}

    We divide the entire charge for the entire time.

Answer5\,\text{А}

Position in this set: 13 from 18

Problem #151

Current, voltage and measuring instruments

Via transverse section conductor for 20 s charge passed 60 class Find force current.

Answer options

  1. 6\,\text{А}
  2. 3\,\text{А}
  3. 1{,}5\,\text{А}
  4. 9\,\text{А}
Show the walkthroughHide the walkthrough
Given
t
20\,\text{с}
q
60\,\text{Кл}
Find

I

  1. I=\frac{q}{t}I=\frac{60}{20}I=3\,\text{А}

    Current shows the charge passed per unit of time.

Answer3\,\text{А}

Position in this set: 14 from 18

Problem #152

Current, voltage and measuring instruments

Via transverse section conductor for 30 s charge passed 120 class Find force current.

Answer options

  1. 8\,\text{А}
  2. 2\,\text{А}
  3. 4\,\text{А}
  4. 12\,\text{А}
Show the walkthroughHide the walkthrough
Given
t
30\,\text{с}
q
120\,\text{Кл}
Find

I

  1. I=\frac{q}{t}I=\frac{120}{30}I=4\,\text{А}

    Current shows the charge passed per unit of time.

Answer4\,\text{А}

Position in this set: 15 from 18

Problem #153

Current, voltage and measuring instruments

Electric current 0{,}5 A constant B current 4 min. Which charge passed by chains?

Answer options

  1. 240\,\text{Кл}
  2. 60\,\text{Кл}
  3. 120\,\text{Кл}
  4. 360\,\text{Кл}
Show the walkthroughHide the walkthrough
Given
I
0{,}5\,\text{А}
t
4\,\text{мин}
Find

q

  1. T=60tT=4 \cdot 60T=240\,\text{с}

    Convert minutes to seconds.

  2. q=ITq=0{,}5 \cdot 240q=120\,\text{Кл}

    With constant current, charge is proportional to time.

Answer120\,\text{Кл}

Position in this set: 16 from 18

Problem #154

Current, voltage and measuring instruments

Electric current 0{,}8 A constant B current 5 min. Which charge passed by chains?

Answer options

  1. 480\,\text{Кл}
  2. 120\,\text{Кл}
  3. 720\,\text{Кл}
  4. 240\,\text{Кл}
Show the walkthroughHide the walkthrough
Given
I
0{,}8\,\text{А}
t
5\,\text{мин}
Find

q

  1. T=60tT=5 \cdot 60T=300\,\text{с}

    Convert minutes to seconds.

  2. q=ITq=0{,}8 \cdot 300q=240\,\text{Кл}

    With constant current, charge is proportional to time.

Answer240\,\text{Кл}

Position in this set: 17 from 18

Problem #155

Current, voltage and measuring instruments

B first 20 with by chains passed current 2 A, then B current 40 with current 5 A. Find average force current for everything time.

Answer options

  1. 8\,\text{А}
  2. 2\,\text{А}
  3. 12\,\text{А}
  4. 4\,\text{А}
Show the walkthroughHide the walkthrough
Given
t_1
20\,\text{с}
I_1
2\,\text{А}
t_2
40\,\text{с}
I_2
5\,\text{А}
Find

I_{\text{ср}}

  1. q_1=I_1t_1q_1=2 \cdot 20q_1=40\,\text{Кл}

    Find the charge of the first gap.

  2. q_2=I_2t_2q_2=5 \cdot 40q_2=200\,\text{Кл}

    Find the charge of the second gap.

  3. I_{\text{ср}}=\frac{q_1+q_2}{t_1+t_2}I_{\text{ср}}=\frac{(40 + 200)}{(20 + 40)}I_{\text{ср}}=4\,\text{А}

    We divide the entire charge for the entire time.

Answer4\,\text{А}

Position in this set: 18 from 18

Problem #156

Current, voltage and measuring instruments

B first 30 with by chains passed current 3 A, then B current 30 with current 7 A. Find average force current for everything time.

Answer options

  1. 5\,\text{А}
  2. 10\,\text{А}
  3. 2{,}5\,\text{А}
  4. 15\,\text{А}
Show the walkthroughHide the walkthrough
Given
t_1
30\,\text{с}
I_1
3\,\text{А}
t_2
30\,\text{с}
I_2
7\,\text{А}
Find

I_{\text{ср}}

  1. q_1=I_1t_1q_1=3 \cdot 30q_1=90\,\text{Кл}

    Find the charge of the first gap.

  2. q_2=I_2t_2q_2=7 \cdot 30q_2=210\,\text{Кл}

    Find the charge of the second gap.

  3. I_{\text{ср}}=\frac{q_1+q_2}{t_1+t_2}I_{\text{ср}}=\frac{(90 + 210)}{(30 + 30)}I_{\text{ср}}=5\,\text{А}

    We divide the entire charge for the entire time.

Answer5\,\text{А}

The theory behind these problems

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

Electric current and circuitConditions for the existence of current, sources, direction and effects of current.Current, voltage and measuring instrumentsAmmeters, voltmeters and safe connections.

Formulas by topic

Look up symbols and units of measurement in the reference.

Timet, τ · сElectric chargeq, Q · КлElectrical voltageU · ВWorkA · ДжElectric currentI · А