Answer:
time=4s
Explanation:
we know that in a RL circuit with a resistance R, an inductance L and a battery of emf E, the current (i) will vary in following fashion
, where
max=
Given that, at i(2)=
⇒
⇒
⇒
Applying logarithm on both sides,
⇒
⇒
⇒
Now substitute 
⇒
⇒
⇒
Applying logarithm on both sides,
⇒
⇒
⇒
now subs. 
⇒
also 
⇒
⇒
Answer:
150J
Explanation:
Formula : <u>Work</u><u> </u><u>done</u>
Force x distance
work done = force x distance
Distance should be measured in meters
300÷100=3m
work done = 450 x 3
=150J
<span>The weightlifter does no work. Although he has exerted force, work is the product of force over distance. Since he has not moved the wall he has done no work.</span>
Explanation:
The charge on the electron is, 
The electric field at a distance r from the electron is :

Where
k is the electrostatic constant, 
We know that the electric field lines starts from positive charge and ends at the negative charge. Also, for a positive charge the field lines are outwards while for a negative charge the field lines are inwards.
So, the correct option is " the electric field is directed toward the electron and has a magnitude of
. Hence, this is the required solution.
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