An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
We can calculate current drawn by electric oven is
Given - Power = 2kW = 2000 W
Potential difference of 220 W by applying the formula P = VI
By putting the value =
The magnetic field in a given region is uniform. Draw a diagram to represent it.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
In Activity 13.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south (b) towards east
(c) downward (d) upward
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
Draw magnetic field lines around a bar magnet.
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
List the properties of magnetic field lines.
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
Why should curd and sour substances not be kept in brass and copper vessels?
What is the far point and near point of the human eye with normal vision?
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
Find the power of a concave lens of focal length 2 m.
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.
In the Modern Periodic Table, which are the metals among the first ten elements?
A solar water heater cannot be used to get hot water on
(a) a sunny day. (b) a cloudy day.
(c) a hot day. (d) a windy day.
What changes would you suggest in your home in order to be environment-friendly?
The magnification produced by a plane mirror is +1. What does this mean?
On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?