CBSE physics
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A point charge Q is placed at point O as shown in the figure. Is the potential difference VA –VB positive, negative, or zero, if Q is (i) positive (ii) negative? 
With increase in distance, potential due to point charge decreases. So,
i) VA - VB is positive when charge Q is positive.
ii) VA - VB is negative.
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A plane electromagnetic wave travels in vacuum along z-direction. What can you say about the direction of electric and magnetic field vectors?
The direction of electric field vectors is along X-axis.
Magnetic field vector is along Y-axis.
A resistance R is connected across a cell of emf 
and internal resistance r. A potentiometer now measures the potential difference between the terminals of the cell as V. Write the expression for 'r' in terms of 
, V and R.
The expression for internal resistance is given by,
The permeability of a magnetic material is 0.9983. Name the type of magnetic materials it represents.
Here, permeability is less than 1 i.e., 
.
So, magnetic material is diamagnetic.
Define the term 'wattless current'.
Current flowing in an ac circuit without any net dissipation of power is called wattless current.
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Mock Test Series
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