Magnetic Effects of Current-2 Flashcards
define electromagnet
A strong magnetic field produced inside a solenoid can be
used to magnetise a piece of magnetic material, like soft iron,
when placed inside the coil (Fig. 13.11). The magnet so formed is
called an electromagnet.
electromagnet is a long tightly wound helical coil of insulated metallic wire on a soft iron core.
what are charcateristics of electromagnet?
the strength of an electromagnet can be increased by:
i) increasing the current flowing through the solenoid
ii) increasing the number of turns in the solenoid.
The polarity of the electromagnet is decided by the direction of flow of current
differentiate between electromagnet and permanent magnet
electromagnet
- It only behaves as a magnet when electric current is passed through the solenoid. It gets demagnetised when we stop the flow of current through the soilenoid. So it is temporary
- generally gives a strong magnetic field.The strength of the electromagnet can be changed. Its strength can be increased/ decreased by increasing or decreasing current through it and toggling amount of turns,
- its polarity can be reversed if the flow of current direction is changed
-pure soft iron core
permanent magnet
- It cannot be demagnetised easily. It has to be heated or thrown repeatedly on the floor.
-The strength of the magnet is quite weak. Neither can its strength be changed,
- Its polarity is permanent and cant be changed,
-hard steel, alnico,nipermag(al,fe,ti)
is there any force acting on a current carrying conductor when placed in a magnetic field?
an electric current flowing through a conductor
produces a magnetic field. The field so produced exerts a force on a
magnet placed in the vicinity of the conductor. French scientist Andre
Marie Ampere (1775–1836) suggested that the magnet must also exert
an equal and opposite force on the current-carrying conductor.
what does the force exerted on the current conductor depend ipin
direction of the force on the conductor depends upon the
direction of current and the direction of the magnetic field.
when the current through the conductor increases, the force also increases
The force exerted on the conductor is the largest when when the direction of current is at right angles to the direction of the magnetic field. The force exerted becomes zero when current is parallel.
state fleming’s left hand rule
stretch the thumb,
forefinger and middle finger of your left hand
such that they are mutually perpendicular
(Fig. 13.13). If the first finger points in the
direction of magnetic field and the second
finger in the direction of current, then the
thumb will point in the direction of motion or
the force acting on the conductor.
Which of the following property of a proton can change while it moves freely in a magnetic field?
The force acting on the proton would change both velocity and momentum.
define direct current
an electric current whose magnitude is constant or variable but the direction of flow of current remains the same is called direct current. Denoted by D.C.
It is supplied by a voltaic cell, dry cell etc.
its frequency is 0 Hz.
define alternating current
An electric current whose magnitude changes with time and direction reverses periodically is called alternating current.
Denoted by A.C.
supplied by powerhouse generators, car alternators
what is frequency?
frequency of ac refers to the number of cycles ac completed in a second. The frequency of ac in india is 50hz. This means that the ac copleted 50 cycles in one second. This means the current reverses direction every 1/100 second. So the current changes its irection 100 times in a second.
what is the advatnage of using ac over dc?
i) cost of generation of ac is much less than cost for dc
ii) ac can be easily converted to dc using a device called rectifier
iii) magnitude of ac current can be changes easily using a choke coil, without involving much loss of energy.
iv) ac can be transmitted over long distances with negligible loss of electric energy than dc.
v) ac can be obtained at any desried voltage using trasnfomer.
define mains
we receive electric power to our house thrught the main suply called mains
what is the
i) live wire
live wire is the eire which has a red colour insulation cover. This is a high voltage wire. It alters its voltage to allow for the reversing direction of alternating current. When the current passes through the live wire, its voltage is negative and lower than that of neutral wire, while when current passes through the neutral wire its voltage is positive and higher than that of neutral wire.
what is neutral wire
it is the wire with a black coloured insulation cover. It has 0 voltage which is nearly close to that of the ground. We will not get chock when we touch the neutral wire
Why do we get shock when we touch live wire
When we touch the live wire, the potential difference across the ground and the live wire will be different. Hence current will pass through us and we will get an electric shock.
