CBSE Class 8 Science Electricity Magnetic and Heating Effects (Class 8 NCERT New) Quiz 7

1. While testing fruits and vegetables for conductivity, a student inserted the copper wire ends of a tester into cut half of potatoes a colour change is observed:

A greenish blue spot around both electrodes B greenish blue spot around the negative electrode C greenish blue spot around the positive electrode D no colour change is seen

2. A chemist had shown that if electrodes were immersedin water, and a current was passed, bubbles of oxygenand hydrogen were produced. This scientist was:

A William Nicholson B Michael Faraday C Alessandero Volta D John Frederic Daniell

3. 2. Why is it better to use a light – emitting diode (LED) rather than a light bulb when testing the electrical conductivity liquids?

A a. An LED glows even when a weak electric current flows in a circuit B b.LEDs do not melt even when a high electric current flows in a circuit C c.LEDs are environment friendly D d. LEDs are cheap

4. 3. Firemen shut off the electricity supply for the area before using water hoses to douse a fire. Why?

A a.To prevent the fireman from being electrocuted because ordinary water is a conductor electricity B b. To prevent electrical devices from being spoilt. C c. To reduce electricity usage D d. To prevent the fire from spreading

5. 4. When an electric current flows through a conducting solution, it can produce which of the following effects?

A a. Bubbles of gas on the electrodes B b. Deposits of metal on the electrodes C c. A change in the colour of the solution D d. All the above.

6. Boojho and Paheli performed experiments taking similar bulbs and cells but two different solutions A and B as shown in the figure.They found that the bulb in the setup A glows more brightly as compared to that of the setup B. You would conclude that

A (a) higher current is flowing through the circuit in setup A. B (b) higher current is flowing through the circuit in setup B. C (c) equal current is flowing through both the circuits. D d) the current flowing through the circuits in the two setups cannot be compared in this manner.

7. In Liquids, Electricity flows because of the movement of

A Protons B Neutrons C Electrons D Ions

8. there are __________ types of effects of electric current

A 5 B 4 C 3 D 2

9. When electric current passes through a conducting solution, it causes _______ _______

A chemical reactions B light effect C magnetic effect D nucleus reaction

10. Who discovered chemical effect of elecric current?

A Thomas Edison B Joule-Lenz C Michael Faraday D James Watt