CBSE Class 7 Science Electricity: Circuits and Their Components (Class 7 NCERT New) Quiz 8

1. In an LED, the current can pass through in how many directions?

A One direction only B Two directions C Any direction D It depends on the battery size

2. Which part of the human body makes it dangerous to touch live electrical wires?

A The body is an insulator. B The body is a conductor of electricity. C The body generates its own DC current. D The body acts as a battery.

3. What is the metal cap on an electric cell?

A The negative terminal B The positive terminal C The insulator D The filament

4. Why can a switch be placed at any point in a simple series circuit to control whether a bulb glows?

A Because opening or closing the switch anywhere in the single path breaks or completes the circuit for all components B Because switches contain their own power source that brightens the bulb wherever they are placed C Because the switch forces current to flow only through the bulb regardless of position D Because switches reduce resistance only near the battery

5. Suppose an insulator like rubber or plastic is inserted between two connection points in a circuit while the switch is ON. Why will the lamp not glow?

A The insulator blocks the flow of current, creating an open circuit B The insulator increases current too much, burning the filament instantly C The insulator redirects current through the battery only D The insulator stores charge and later releases it to the lamp

6. In a series circuit with two bulbs, one filament breaks. Why does the other bulb stop glowing as well?

A The broken filament opens the single path, so no current flows through either bulb B The remaining bulb draws too much current and turns off automatically C The battery reverses polarity when one filament breaks D The switch becomes nonfunctional when any bulb fails

7. If wire ends are not stripped and the plastic insulation is left on at the connection points, why won’t the lamp glow?

A The insulation prevents metal-to-metal contact, so the circuit remains open B The insulation heats the wire so the bulb stays off until it cools C The insulation reverses the current direction through the bulb D The insulation shorts the battery and protects the bulb

8. When battery markings are faded, how can you identify the positive and negative terminals of a typical cell?

A The positive terminal is the raised metal cap and the negative terminal is the flat end B The positive terminal is the heavier end and the negative terminal is lighter C The positive terminal feels warmer to the touch than the negative D The positive terminal is always painted red and the negative black

9. You have six cells, some functional and some not. Which approach best tests which cells work?

A Build a simple circuit with a bulb (or LED), holder, and wires; insert one cell at a time with correct polarity and observe if the bulb lights B Shake each cell and keep the ones that rattle least C Measure the cells’ mass and keep the heaviest ones D Connect all six cells in series at once and choose the ones closest to the switch

10. Why does an LED require correct polarity to glow while an incandescent bulb works regardless of terminal orientation?

A An LED is a diode that allows current in only one direction; a filament bulb is nonpolar and conducts in either direction B An LED contains a tiny switch that turns on only with left-to-right current; a bulb contains two switches C An LED has no resistance, so polarity is needed to limit current; a bulb has infinite resistance D An LED needs alternating current, but a bulb needs direct current only