Resistance in Series and Parallel · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

One path or many paths

Science · Energy · ages 14-16
Name ______________________   Date ____________

  1. In series, the same current flows through every resistor.

    Circle one:   True   False

  2. Two 10 ohm resistors sit in series. What is the total?

    • 20 ohms
    • 10 ohms
    • 5 ohms

  3. Two matching resistors are rewired from series into parallel. What happens to the total resistance?

    • It doubles
    • It stays the same
    • It falls well below one of them

  4. A lamp is added in parallel to a circuit. What happens to the supply current?

    • It falls, because voltage splits
    • It rises, because total resistance falls
    • It stays exactly the same

  5. Resistors of 4 ohms, 6 ohms and 10 ohms sit in series. What is the total in ohms? Type the number.

    Answer: ______________

  6. You want to measure the current through a resistor. Where does the ammeter go?

    • Across the resistor
    • In series with the resistor
    • Across the supply

  7. A learner says adding a parallel lamp raises total resistance, since there is more to push through. What is the mistake?

    • Voltage splits across parallel branches
    • Parallel adds a path, so total resistance falls
    • Current is used up by the first lamp

  8. One bulb in an old series string of lights fails. What happens, and why?

    • The rest glow brighter
    • All stay on, because voltage is shared
    • All go out, because the single path is broken
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Answer key

For grown-ups. Fold this page away before handing over the rest.

One path or many paths W1-mt_B29m3h5B75-s1

  1. True · One path means one current everywhere in it.
  2. 20 ohms · Series totals are the plain sum: 10 plus 10 is 20.
  3. It falls well below one of them · Extra paths always cut the total below the smallest branch.
  4. It rises, because total resistance falls · A new branch lowers total resistance, so the supply pushes more current.
  5. 20 · Add all three: 4 plus 6 plus 10 is 20.
  6. In series with the resistor · An ammeter must carry the current, so it joins the path in series.
  7. Parallel adds a path, so total resistance falls · More paths make the push easier, never harder.
  8. All go out, because the single path is broken · One broken link kills the only path, so every bulb dies.
Worksheet · LightMySky