Mix Examples - Magnetic Effects of Electric Current Questions in English

(B) The statement is $False$. An electric motor is a device that converts electrical energy into mechanical energy. Conversely,an electric generator is a device that converts mechanical energy into electrical energy.

(B) The statement is $False$.
Fleming's right-hand rule is used to determine the direction of the induced current in a conductor moving within a magnetic field.
The direction of the magnetic field around a current-carrying conductor is determined by the Right-Hand Thumb Rule (also known as Maxwell's Right-Hand Grip Rule).

(A) An electric generator is a device that converts mechanical energy into electrical energy. It operates based on the principle of electromagnetic induction,which states that a changing magnetic flux through a coil induces an electromotive force $(EMF)$ or current in the coil. When the coil rotates within a magnetic field,the magnetic flux linked with it changes,thereby inducing an electric current.

(B) The statement is $False$.
Electric current that flows in a single direction is known as $Direct \ Current$ $(DC)$.
$Alternating \ Current$ $(AC)$ is the current that periodically reverses its direction.

(A) In domestic electrical circuits,the standard colour coding for wires is as follows:
$1$. The $Live$ wire is red.
$2$. The $Neutral$ wire is black.
$3$. The $Earth$ wire is green.
Therefore,the statement is $True$.

(A) In domestic electrical circuits,all appliances are connected in parallel.
This is because parallel circuits ensure that each appliance receives the same voltage ($220 \ V$ in India) regardless of the number of appliances connected.
Additionally,if one appliance fails or is switched off,it does not affect the operation of other appliances,and each appliance can be controlled by its own individual switch.

(A) Rubber is an insulator,meaning it does not allow electric current to flow through it. By wearing rubber gloves and rubber shoes,a person creates a high-resistance barrier that prevents electricity from passing through the body to the ground,thereby protecting the individual from electric shocks.

(A) Earthing is a safety measure used to protect users from electric shocks. It involves connecting the metallic body of an electrical appliance to the ground through a wire. If there is any leakage of current in the appliance,the current flows directly to the earth instead of passing through the user's body,thereby preventing a fatal electric shock.

(B) The fundamental law of magnetism states that like magnetic poles (North-North or South-South) repel each other,while unlike magnetic poles (North-South) attract each other. Therefore,the given statement is false.

(B) The statement is $False$. When a magnetic material is magnetized by contact with a magnet,the pole induced at the point of contact is always the opposite of the pole used for magnetization. Therefore,if a metallic knife is stroked against the north pole of a bar magnet,the point of contact on the knife will develop a south pole,not a north pole.

(A) The magnetic field lines produced by a current-carrying straight wire are concentric circles around the wire. Unlike a bar magnet,which has distinct North and South poles,a magnetic field generated by a straight current-carrying conductor does not have defined poles. Therefore,the statement is True.

(B) The statement is False.
An electric generator is a device that converts mechanical energy into electrical energy.
Conversely,an electric motor is a device that converts electrical energy into mechanical energy.

(A) Magnetic field lines are imaginary lines used to represent the magnetic field.
Outside a bar magnet,the magnetic field lines always emerge from the North $(N)$ pole and enter the South $(S)$ pole.
Inside the magnet,the field lines travel from the South $(S)$ pole to the North $(N)$ pole,forming continuous closed loops.
Therefore,the correct direction outside the magnet is from the $N$-pole towards the $S$-pole.

(D) Magnetic field lines are imaginary lines that represent the magnetic field.
Properties of magnetic field lines include:
$1$. They emerge from the $N$ pole and enter the $S$ pole outside the magnet,making their direction $N$ to $S$.
$2$. They form continuous closed loops.
$3$. The closeness of the lines indicates the strength of the magnetic field; closer lines mean a stronger field.
$4$. Two magnetic field lines can never cross each other because if they did,there would be two directions for the magnetic field at the point of intersection,which is physically impossible.
Therefore,the statement that magnetic field lines can cross each other is false.

(D) magnetic needle (or compass needle) is a small magnet that aligns itself with the direction of a magnetic field.
When placed in a region where a magnetic field exists,the magnetic needle experiences a torque and deflects from its original position.
This deflection indicates the presence of a magnetic field.
While a galvanometer can also detect small currents,the most direct and fundamental instrument used to detect the presence of a magnetic field is a magnetic needle.

(B) In $1820$,the Danish physicist $Hans$ $Christian$ $Oersted$ observed that a magnetic compass needle gets deflected when placed near a current-carrying wire. This observation demonstrated that an electric current produces a magnetic field around it,which is known as the magnetic effect of electric current.

(C) The direction of the magnetic field produced by a current-carrying conductor is determined by the $Right$ $hand$ $thumb$ $rule$.
According to this rule,if you hold a current-carrying straight conductor in your right hand such that your thumb stretches along the direction of the current,then your fingers will wrap around the conductor in the direction of the magnetic field lines.

(A) The Right-Hand Thumb Rule states that if you hold a current-carrying straight conductor in your right hand such that your thumb points in the direction of the electric current,then your fingers wrapped around the conductor will show the direction of the magnetic field lines. Therefore,the thumb indicates the direction of the electric current.

(C) When an electric current flows through a straight conducting wire,it generates a magnetic field around it. According to the Right-Hand Thumb Rule,the magnetic field lines are represented as concentric circles centered on the wire. Therefore,the magnetic field produced is circular around the wire.

(B) As we move away from the wire of a current-carrying circular loop,the concentric circles representing the magnetic field lines become larger and larger.
At the center of the circular loop,the arcs of these large circles appear as straight lines.
Therefore,the magnetic field lines passing through the center of a current-carrying circular loop are straight lines.

(C) current-carrying solenoid consists of a long coil of many circular turns of insulated copper wire wrapped in a cylindrical form.
When current flows through the solenoid,it produces a magnetic field pattern that is identical to that of a bar magnet.
The magnetic field lines emerge from one end (acting as the North pole) and enter the other end (acting as the South pole),forming closed loops both inside and outside the solenoid,just like a bar magnet.

(A) The principle of electromagnetic induction was discovered by $Michael \ Faraday$ in $1831$.
He demonstrated that a changing magnetic field induces an electromotive force $(EMF)$ or current in a conductor.
Therefore, the correct option is $A$.

(C) The magnetic force $(F)$ acting on a current-carrying conductor of length $(l)$ carrying current $(I)$ placed in a magnetic field $(B)$ is given by the vector product: $F = I(l \times B)$.
According to the right-hand rule or Fleming's left-hand rule,the direction of the magnetic force is always perpendicular to the plane containing both the direction of the electric current and the direction of the magnetic field.
Therefore,the force is perpendicular to both the magnetic field and the electric current.

(A) The magnetic force $F$ acting on a current-carrying wire of length $L$ carrying current $I$ in a magnetic field $B$ is given by the formula: $F = I L B \sin(\theta)$,where $\theta$ is the angle between the direction of the current and the magnetic field.
For the magnetic force to be zero $(F = 0)$,the value of $\sin(\theta)$ must be zero.
This occurs when $\theta = 0^{\circ}$ or $\theta = 180^{\circ}$.
Therefore,when the current-carrying wire is placed parallel to the magnetic field,the magnetic field does not exert any force on it.

(D) According to Faraday's law of electromagnetic induction,an induced current is produced in a loop only when there is a change in the magnetic flux linked with the loop.
Magnetic flux $\phi = B \cdot A \cdot \cos(\theta)$.
In cases $A$,$B$,and $C$,there is a relative motion between the magnet and the loop,which causes a change in the magnetic field $B$ passing through the loop,thereby changing the magnetic flux and inducing a current.
In case $D$,both the loop and the magnet are moving in the same direction with the same speed. Therefore,there is no relative motion between them.
Since there is no relative motion,the magnetic flux linked with the loop remains constant.
As there is no change in magnetic flux,no induced current will be obtained in the loop.

(B) An $Electric \text{ } motor$ is a device that converts electrical energy into mechanical energy.
It works on the principle of the magnetic effect of electric current, where a current-carrying coil placed in a magnetic field experiences a force that causes it to rotate.
In contrast, an $Electric \text{ } generator$ converts mechanical energy into electrical energy.
$Electric \text{ } iron$ and $Electric \text{ } oven$ convert electrical energy into heat energy.

(C) An electric generator works on the principle of $Electromagnetic \text{ } Induction$.
It converts mechanical energy into electrical energy by rotating a coil within a magnetic field, which induces an electric current.

(C) In India,the standard domestic power supply provided by the electricity grid is an alternating current $(AC)$ with a root mean square $(RMS)$ voltage magnitude of $220 \ V$.
The frequency of this alternating current is standardized at $50 \ Hz$,which means the current changes its direction $100$ times per second (completing $50$ cycles per second).
Therefore,the correct values are $220 \ V$ and $50 \ Hz$.

(C) In domestic electrical circuits,different colours of insulation are used for wires to distinguish them.
$1$. The live wire is typically red.
$2$. The neutral wire is typically black.
$3$. The earth wire is traditionally green or yellow-green.
Therefore,green insulation is used for earthing to ensure safety by providing a low-resistance path for leakage current.

(A) battery is a device that converts chemical energy into electrical energy.
It produces a steady flow of electrons in a single direction,which is known as Direct Current $(DC)$.
Unlike Alternating Current $(AC)$,which periodically reverses its direction,the current from a battery remains constant in its polarity and direction over time.
Therefore,the correct option is $A$.

(B) $Galvanometer$ is an electromechanical instrument used for detecting and indicating an electric current.
It works on the principle that a magnetic field exerts a torque on a current-carrying coil placed within it.
When a small current flows through the coil,it deflects,indicating the presence and direction of the current.
In contrast,a $Voltmeter$ measures potential difference,a $Fuse$ is a safety device,and a $Battery$ is a source of electric energy.

(A) An electric fuse is a safety device used in electrical circuits to prevent damage from excessive current.
It consists of a wire made of a material with a low melting point (such as an alloy of lead and tin).
When the current in the circuit exceeds a safe limit,the heat generated causes the fuse wire to melt and break the circuit,thereby protecting the appliances.
Therefore,a fuse is a conductor with a low melting point.

(B) Fleming's Right-Hand Rule is used to determine the direction of the induced current in a conductor moving in a magnetic field.
According to this rule,if you stretch the thumb,forefinger,and middle finger of your right hand such that they are mutually perpendicular to each other,then the thumb points in the direction of the motion of the conductor,the forefinger points in the direction of the magnetic field,and the middle finger points in the direction of the induced current.

(C) The frequency of an $AC$ current is defined as the number of complete cycles per second.
One complete cycle consists of two alternations (or half-cycles) where the current flows in one direction and then in the opposite direction.
Therefore,in one complete cycle,the current changes its direction twice.
Given that the frequency is $50\, Hz$,there are $50$ complete cycles in one second.
Total number of direction changes $= 50 \times 2 = 100$ times per second.

(A) The magnetic field $B$ at the centre of a circular current-carrying coil is given by the formula $B = \frac{\mu_0 I}{2R}$,where $\mu_0$ is the permeability of free space,$I$ is the current,and $R$ is the radius of the coil.
Since the current $I$ is equal for all rings,the magnetic field $B$ is inversely proportional to the radius $R$ of the ring $(B \propto \frac{1}{R})$.
Therefore,the smaller the radius $R$,the larger the magnetic field $B$ at the centre.
Thus,the ring with the smallest radius will have the maximum magnetic field at its centre.

(B) Michael Faraday discovered the phenomenon of electromagnetic induction in $1831$. He demonstrated that a changing magnetic field can induce an electric current in a conductor. This principle is the basis for the operation of electric generators and transformers.

(C) Electromagnetism is the branch of physics that deals with the study of electromagnetic force,a type of physical interaction that occurs between electrically charged particles. It encompasses the study of both electricity and magnetism,as they are fundamentally linked phenomena. When electric charges are in motion,they create magnetic fields,and changing magnetic fields can induce electric currents,which is the core principle of electromagnetism.

(A) Magnetic field lines are continuous closed loops.
Outside the magnet,the field lines emerge from the $N$-pole and merge into the $S$-pole.
Inside the magnet,the direction of the magnetic field lines is from the $S$-pole to the $N$-pole to complete the closed loop.
Therefore,the correct direction inside the magnet is from $S$ to $N$.

(B) The strength of a magnetic field is represented by the degree of closeness of the magnetic field lines.
If the magnetic field lines are crowded or close to each other,it indicates a strong magnetic field.
Conversely,if the field lines are far apart,it indicates a weak magnetic field.
Therefore,in a region where magnetic field lines are close to each other,the magnetic field is strong.

(C) Magnetic field lines are continuous closed loops.
Outside the magnet,the field lines emerge from the $N$ pole and enter the $S$ pole.
Inside the magnet,the field lines are directed from the $S$ pole to the $N$ pole to complete the closed loop.
Therefore,the statement that they are directed from the $N$ pole to the $S$ pole inside the magnet is incorrect.

(B) When an electric current passes through a conductor,it creates a magnetic field around the conductor. This phenomenon is known as the magnetic effect of electric current,first observed by Hans Christian Oersted. The strength and direction of the magnetic field depend on the magnitude and direction of the current flowing through the wire.

(C) According to the Biot-Savart Law,the magnetic field $B$ produced by a long straight current-carrying wire at a distance $r$ is given by the formula $B = \frac{\mu_0 I}{2 \pi r}$.
From this expression,it is clear that the magnetic field $B$ is inversely proportional to the distance $r$ from the wire $(B \propto \frac{1}{r})$.
Therefore,as the distance from the wire increases,the magnetic field decreases in inverse proportion to the distance.

(B) According to the Biot-Savart Law or the right-hand thumb rule application for a straight current-carrying conductor,the magnitude of the magnetic field $B$ at a distance $r$ from the conductor is given by the formula $B = \frac{\mu_0 I}{2 \pi r}$.
From this expression,it is clear that the magnetic field $B$ is directly proportional to the current $I$ $(B \propto I)$ and inversely proportional to the perpendicular distance $r$ from the conductor $(B \propto \frac{1}{r})$.
Therefore,the magnetic field is inversely proportional to the distance from the conductor.

(B) According to the Right-Hand Thumb Rule,if you hold a current-carrying straight conductor in your right hand such that your thumb points in the direction of the current,then your fingers will wrap around the conductor in the direction of the magnetic field lines. Therefore,the direction of the magnetic field is determined by the direction of the electric current flowing through the wire.

(B) The magnetic field $B$ at the center of a circular loop of radius $R$ carrying a current $I$ with $N$ turns is given by the formula: $B = \frac{\mu_0 N I}{2R}$.
From this formula,it is clear that the magnetic field $B$ is directly proportional to the current $I$ and the number of turns $N$,and inversely proportional to the radius $R$ of the loop.
Therefore,the magnetic field at the center is inversely proportional to the radius of the loop.

(C) The magnetic field $B$ at the center of a circular loop carrying current $I$ with radius $r$ and $N$ turns is given by the formula: $B = \frac{\mu_0 N I}{2r}$.
From this formula,it is clear that the magnetic field $B$ is directly proportional to the number of turns $N$ $(B \propto N)$.
If the number of turns increases from $1$ to $6$,the magnetic field will also increase by a factor of $6$.
Therefore,the magnetic field becomes $6$ times stronger.

(C) coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a $Solenoid$.
When an electric current flows through the $Solenoid$,it produces a magnetic field similar to that of a bar magnet.
The magnetic field lines inside the $Solenoid$ are parallel to each other,indicating a uniform magnetic field.

(C) current-carrying solenoid behaves exactly like a bar magnet. The magnetic field lines inside a solenoid are parallel to the axis,indicating a uniform magnetic field. When a soft iron rod is placed inside,it becomes an electromagnet. The pattern of magnetic field lines for a solenoid is identical to that of a bar magnet,not different. Therefore,statement $C$ is incorrect.

(A) When a soft iron rod is placed inside a solenoid,it acts as a core.
Soft iron is a ferromagnetic material,which gets easily magnetized by the magnetic field produced by the current flowing through the solenoid.
This induced magnetism adds to the magnetic field of the solenoid,making the overall magnetic field significantly stronger.
This arrangement is commonly used to create an electromagnet.

(B) Inside a current-carrying solenoid,the magnetic field lines are parallel to each other and to the axis of the solenoid. This indicates that the magnetic field is uniform at all points inside the solenoid. Therefore,the correct option is $B$.