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Physics Chapter 12 : Topic 4
Magnetic Flux Density
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Magnetic flux density is defined as:
Reasoning: Magnetic flux density is the force experienced by a conductor carrying unit current and having unit length placed at $\mathbf{90}^{\mathbf{o}}$ to the magnetic field.
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The symbol commonly used for magnetic flux density is:
Reasoning: Magnetic flux density is represented by the symbol $\mathbf{B}$.
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The equation for magnetic flux density is:
Reasoning: From $\mathbf{F = BIL}$ for a conductor at right angles to the field, $\mathbf{B = F/IL}$.
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The SI unit of magnetic flux density is:
Reasoning: Magnetic flux density is measured in tesla $\mathbf{(T)}$.
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One tesla is equal to:
Reasoning: From $\mathbf{B = F\ /\ IL}$, the unit is $\mathbf{N\ /\ (Am)}$.
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A magnetic flux density of $\mathbf{1\ T}$ means that:
Reasoning: This is the definition of one tesla.
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In the definition of magnetic flux density, the wire must be placed:
Reasoning: The definition uses the maximum force condition where the conductor is perpendicular to the field.
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Magnetic flux density indicates:
Reasoning: Greater magnetic flux density means a stronger magnetic field.
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If the force on a wire increases while current and length remain constant, the magnetic flux density:
Reasoning: Since $\mathbf{B = F\ /\ IL}$, increasing force increases magnetic flux density.
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A conductor of length $\mathbf{2\ m}$ carrying $\mathbf{3\ A}$ current experiences a force of $\mathbf{6\ N}$ in a perpendicular magnetic field. The magnetic flux density is:
Reasoning: $\mathbf{B = F\ /\ IL}$ $\mathbf{= 6\ /\ (3 \times 2)}$ $\mathbf{= 1\ T}$
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A wire carrying current in a magnetic field experiences maximum force when:
Reasoning: Maximum force occurs at $\mathbf{90}^{\mathbf{o}}$, which is the condition used to define magnetic flux density.
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If the length of the conductor is doubled while force and current remain constant, magnetic flux density becomes:
Reasoning: $\mathbf{B = F\ /\ IL}$, so increasing $\mathbf{L}$ reduces $\mathbf{B}$ if $\mathbf{F}$ and $\mathbf{I}$ are constant.
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If the current in a wire is doubled while force and length remain constant, magnetic flux density:
Reasoning: $\mathbf{(B)}$ is inversely proportional to current when force is fixed.
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Magnetic flux density is a measure of:
Reasoning: It describes how strongly a magnetic field interacts with a current-carrying conductor.
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Which equation is valid for a conductor placed at right angles to a magnetic field?
Reasoning: At $\mathbf{90}^{\mathbf{o}}$, $\mathbf{sin\ }\mathbf{\theta}\mathbf{= 1}$, so $\mathbf{F = BIL}$.
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A magnetic field with greater flux density will exert:
Reasoning: Force is directly proportional to magnetic flux density.
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Which quantity is NOT required to determine magnetic flux density using $\mathbf{B = F\ /\ IL}$?
Reasoning: Resistance does not appear in the equation for magnetic flux density.
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A wire carrying $\mathbf{4\ A}$ current and having length $\mathbf{0.5\ m}$ experiences a force of $\mathbf{2\ N}$. The magnetic flux density is:
Reasoning: $\mathbf{B = F\ /\ IL}\mathbf{= 2\ /\ (4 \times 0.5) = 1\ T}$
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Magnetic flux density differs from magnetic force because:
Reasoning: Magnetic flux density describes the magnetic field; force is produced when current interacts with it.
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If a wire is moved from a weak magnetic field to a stronger magnetic field, keeping current and length constant, the force:
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A magnetic flux density of $\mathbf{0\ T}$ indicates:
Reasoning: Zero flux density means no magnetic field strength at that location.
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The direction of magnetic flux density is determined by:
Reasoning: Magnetic flux density is a vector quantity with direction along magnetic field lines.
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If a wire is not perpendicular to the magnetic field, the force equation becomes:
Reasoning: The general equation includes the angle between current and field.
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A conductor experiences maximum force in a magnetic field because:
Reasoning: At $\mathbf{90}^{\mathbf{o}}$, the component of current perpendicular to the field is maximum.
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A $\mathbf{2\ T}$ magnetic field means:
Reasoning: Using $\mathbf{F = BIL}$ $\mathbf{\Longrightarrow}$ $\mathbf{F}\mathbf{= 2 \times 1 \times 1 = 2\ N}$
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Which change will increase the force on a wire without changing magnetic flux density?
Reasoning: Force increases with current according to $\mathbf{F = BIL}$.
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Magnetic flux density is classified as a vector quantity because it has:
Reasoning: Magnetic flux density has both strength and direction.
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A wire carrying current is used to measure magnetic flux density because:
Reasoning: Measuring force allows calculation of $\mathbf{B}$ using $\mathbf{B = F\ /\ IL}$.
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If two magnetic fields have flux densities $\mathbf{2\ T}$ and $\mathbf{5\ T}$, the second field is:
Reasoning: Strength comparison $\mathbf{= 5\ /\ 2 = 2.5}$
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The definition of magnetic flux density is based on:
Reasoning: Magnetic flux density is defined using the force on a wire carrying unit current and having unit length at $\mathbf{90}^{\mathbf{o}}$ to the field.
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