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9th grade · Science · Unit 5 of 7

Electric Current

Circuits, Ohm's law and safety

What your child practices

Static electricity, current, voltage and resistance, solving V = I × R, series and parallel circuits, electrical safety, and electricity generation in BC.

Minnesota K-12 Academic Standards benchmark: 9P.1.2.1.1; 9P.3.1.1.2 · electric current, circuits and magnetic fields

How we explain it

Children can open this short lesson before they practice.

  1. Current is the flow of charge. Voltage is the push. Resistance slows the flow.
  2. Ohm’s law: V = I × R. Energy = power × time (E = P × t).
  3. Homes are wired in parallel so each device works on its own.

Example: A 60 W lamp runs for 4 hours. How many watt-hours does it use? E = P × t. 60 × 4 = 240. Answer: 240 Wh

Electric Current in Minnesota

In the Minnesota K-12 Academic Standards, this is unit 5 of 7 in 9th grade Science, after Electrons & Compounds and before Photosynthesis & Respiration.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Minnesota Department of Education (MDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    A device rated 50 W runs for 4 hours. How many watt-hours of energy does it use? (E = P × t)

    answer boxWh

  2. Question 2

    Houses are wired in parallel because…

    • it uses less metal
    • series circuits do not work
    • each device can work independently on the full voltage
    • it makes bulbs dimmer

  3. Question 3

    A switch turns off a circuit by…

    • removing the battery's voltage
    • increasing the resistance to zero
    • creating a gap so current cannot flow
    • making the wire longer

  4. Question 4

    In a series circuit, if one bulb burns out…

    • the other bulbs get brighter
    • the battery stops
    • nothing changes
    • the other bulbs go out too

  5. Question 5

    Two resistors, 5 Ω and 3 Ω, are connected in series. What is the total resistance?

    answer boxΩ

  6. Question 6

    A battery supplies 70 V to a resistor of 10 Ω. What is the current in amperes? (I = V ÷ R)

    answer boxA

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