Tag: physics
Questions Related to physics
When cathode rays moving horizontally pass through an electric field directed vertically downward, the rays would be deflected ________ .
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downward
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upward
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backward
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none of the above
The electric field is directed vertically downward i.e. the upper plate is positively charged and the lower plate is negatively charged . Because $ \vec{E} $ points in a direction from positive to negative.
When a cathode ray particle i.e. negatively charged particle enters the electric field, it will be following a parabolic trajectory and would be directed towards the positive plate. Since the positive plate is upward directed. So cathode ray will be directed upwards.
When a charged particle of charge $x\ C$ moves through a potential difference of $y\ V$, the gain in kinetic energy is equal to $xy \ J$.
An electron and an alpha particle have their masses in the ratio of 1 : 7200 and charges in the ratio of 1 : 2. If they start moving from rest through the same electrical potential difference then the ratio of their velocities will be ______.
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1 : 60
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60 : 1
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1 : 20
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20 : 1
Given : If particle has charge $x$ coulombs and potential difference $ y $ volts . Then gain in K.E. = $ xy $ joules.
Using similar analysis,
$ \dfrac{\text{(mass)electron}}{\text{(mass) alpha particle}} = \dfrac{1}{7200} $
$ \dfrac{\text{(charge)electron}}{\text{(charge) alpha particle}} = \dfrac{1}{2} $
We need to find $ \dfrac{\text{(velocity)electron}}{\text{(velocity) \alpha particle}} $
Since initially there at rest, initial K.E. = 0;
They move through same potential difference. Let potential difference be $ y $ volts.
So, gain in K.E = Final K.E – Initial K.E
= Final K.E – 0
So, gain in K.E = $ charge \times potential \, difference $
Ratio of gain in K.E of electron and $\alpha$ particle = Ratio of final K.E of electron and $\alpha$ particle
$ \dfrac{\dfrac{1}{2} m v _e^2 \times y}{\dfrac{1}{2} m v _\alpha^2 \times y} $
$ = \dfrac{1}{2} \times 7200 = 3600 $
$ \dfrac{v _e}{v _\alpha} = \sqrt{3600} = 60 $
Why one should never touch electrical appliance with wet hand?
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Wet body is bad conductor
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Wet body is good conductor
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Both of these
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None of these
Never touch any electrical appliance with wet hands. Wet body can act as a good conductor of electricity. In case of any leakage the person with wet hands will get shock.
The effect of current on which the use of a fuse is based is
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Magnetic effect
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Chemical effect
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Heating effect
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Induction effect
Heating effect of current is used in fuse.
Which of the following are correct safety precautions to be taken while using electricity?
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Don't yank an electrical cord from the wall.
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Fly your kite far away from power lines or substations.
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Do look up and look out for power lines before you climb a tree.
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All of these
Identify correct option safety precaution while using electricity
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Don't plug a bunch of stuff into one outlet or extension cord.
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Make sure all electric cords are tucked away, neat and tidy.
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Don't ever climb the fence around an electrical substation.
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All of these
Major dangers while using electricity are/is
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Fire
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An electric shock
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Both
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None
A) Fire
B) An electric shock.
i) Poor insulation of wires,
ii) Touching the appliances with wet hands and
iii) No earthing of the appliance.
Which of the following are safety precautions to be taken while using electricity. Select correct option
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Avoid water at all times when working with electricity
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Never use equipment with frayed cords, damaged insulation or broken plugs
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Always use insulated tools while working.
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All of these
water can damage the circuits. it can also create a short circuit which may result into serious accidents. If insulation is damaged, then our body may come into direct contact with the electric current, resulting in an electric shock. Insulation is thus compulsory while working with electricity.
Mark the incorrect option
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The appliances must have its metallic case earthed
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The appliances must be provided with a fuse
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The appliance should always operated(or touched)with wet hands
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All
Touching an appliance with wet hands can cause an electric shock, thus option C is the incorrect statement.
Following are some precaution to be taken while using electricity given as options. Mark most appropriate one.
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Have a grown-up put safety caps on all unused electrical outlets.
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Remind your mom or dad to watch out for power lines
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Keep electrical stuff far away from water.
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All of these