የምዕራፍ ማስታወሻዎችና የመልመጃ ጥያቄዎች

የ12ኛ ክፍል ፊዚክስ ምዕራፍ 4፦ ኤሌክትሮማግኔቲዝም

በዚህ ገጽ ያለው ሁሉ ለ12ኛ ክፍል የፊዚክስ መፅሐፍ ምዕራፍ 4 ነው፦ ምዕራፉ የሚሸፍነው፣ አጭር ማስታወሻዎቹ፣ የመልመጃ ጥያቄዎች ከመልሶቻቸው ጋር፣ እና ቪዲዮ ባለበት የትምህርቱ ቪዲዮ።

5
ካርዶች: 10
የምዕራፍ 4 የመልመጃ ጥያቄዎች: 118–142
የምዕራፍ 4 የመፅሐፍ ገጾች

ምዕራፍ 4 የሚሸፍነው

1.Magnets and Magnetic field
2.Magnetic field lines
3.Current and Magnetism
4.Electromagnetic Induction
5.Faraday's Law of electromagnetic Induction
6.Transformers
7.Application and safety

የምዕራፍ 4 አጭር ማስታወሻዎች

በ12ኛ ክፍል የፊዚክስ ገጽ ላይ በዚህ ምዕራፍ ሥር የተመዘገቡት ካርዶች። አንድ በአንድ ይክፈቱ።

የFaraday የኢንደክሽን ህግቀመር

\varepsilon = -N \frac{\Delta\Phi_B}{\Delta t}

\varepsilon = -N \frac{\Delta\Phi_B}{\Delta t}

$\varepsilon$: የተፈጠረ የኤሌክትሮሞቲቭ ኃይል $\text{V}$
$N$: በኮይል ውስጥ ያሉ የዙሮች ብዛት $1$
$\Delta\Phi_B$: የማግኔቲክ ፍላክስ ለውጥ $\text{Wb}$
$\Delta t$: የጊዜ ለውጥ $\text{s}$

መቼ እንደሚጠቀሙበት

በሚለዋወጥ magnetic flux ምክንያት በኮይል ውስጥ የሚፈጠረውን induced electromotive force ለማስላት ይጠቀሙበት።

ይጠንቀቁ

አሉታዊ ምልክቱ የLenz ህግን ያሳያል፤ ይህም induced emf የflux ለውጡን እንደሚቃወም ያሳያል።

ከGrade 12 Physics፣ ገጽ 118-142 የተዘጋጀ፤ ከመውጣቱ በፊት ሁለት ጊዜ ተረጋግጧል

የቀጥተኛ ሽቦ magnetic fieldቀመር

B = \frac{\mu_0 I}{2\pi r}

B = \frac{\mu_0 I}{2\pi r}

$B$: ማግኔቲክ መስክ $\text{T}$
$\mu_0$: የነፃ ቦታ ፐርሚአቢሊቲ $\text{T}\cdot\text{m}\cdot\text{A}^{-1}$
$I$: የኤሌክትሪክ ፍሰት $\text{A}$
$r$: ከሽቦው ያለው ርቀት $\text{m}$

መቼ እንደሚጠቀሙበት

የኤሌክትሪክ current ከሚሸከም ረጅም ቀጥተኛ ሽቦ በተወሰነ ርቀት ላይ ያለውን የmagnetic field መጠን ለማስላት ይጠቀሙበት።

ይጠንቀቁ

ርቀት r በሜትር እንጂ በሴንቲሜትር ወይም በሚሊሜትር መሆን የለበትም።

ከGrade 12 Physics፣ ገጽ 118-142 የተዘጋጀ፤ ከመውጣቱ በፊት ሁለት ጊዜ ተረጋግጧል

Magnetic Fluxቀመር

\Phi_B = B A \cos\theta

\Phi_B = B A \cos\theta

$\Phi_B$: ማግኔቲክ ፍላክስ $\text{Wb}$
$B$: ማግኔቲክ መስክ $\text{T}$
$A$: ስፋት $\text{m}^2$
$\theta$: በማግኔቲክ መስክ እና ለስፋቱ ኖርማል በሆነው መስመር መካከል ያለው ማዕዘን $\text{degrees}$

መቼ እንደሚጠቀሙበት

በmagnetic field ውስጥ በተቀመጠ ወለል ውስጥ የሚያልፈውን ጠቅላላ magnetic flux ለማስላት ይጠቀሙበት።

ይጠንቀቁ

አንግል theta የሚለካው በmagnetic field እና በarea normal መካከል እንጂ በገጹ ወለል እና በfieldዱ መካከል አይደለም።

ከGrade 12 Physics፣ ገጽ 118-142 የተዘጋጀ፤ ከመውጣቱ በፊት ሁለት ጊዜ ተረጋግጧል

በMagnetic Flux ስሌት ውስጥ የወለል አንግል ስህተትየተለመደ ስህተት

መቼ እንደሚጠቀሙበት

ጥያቄው በmagnetic field እና በሉፑ ወለል መካከል ያለውን አንግል ሲሰጥ ይጠቀሙበት።

ይጠንቀቁ

ጥያቄው ከገጹ ወለል ጋር ያለውን አንግል ከሰጠ፣ በflux ቀመር ውስጥ ለtheta ለመጠቀም 90 ሲቀነስ የተሰጠውን አንግል ማስላት አለብዎት።

ከGrade 12 Physics፣ ገጽ 118-142 የተዘጋጀ፤ ከመውጣቱ በፊት ሁለት ጊዜ ተረጋግጧል

የTransformer የዙር ጥምርታቀመር

\frac{N_p}{N_s} = \frac{V_p}{V_s}

\frac{N_p}{N_s} = \frac{V_p}{V_s}

$N_p$: የመጀመሪያ ደረጃ ኮይል ዙሮች $1$
$N_s$: የሁለተኛ ደረጃ ኮይል ዙሮች $1$
$V_p$: የመጀመሪያ ደረጃ ቮልቴጅ $\text{V}$
$V_s$: የሁለተኛ ደረጃ ቮልቴጅ $\text{V}$

መቼ እንደሚጠቀሙበት

በአማካኝ ተለዋዋጭ current ትራንስፎርመር ውስጥ primary እና secondary ቮልቴጆችን ከዙር ብዛት ጋር ለማዛመድ ይጠቀሙበት።

ይጠንቀቁ

ትራንስፎርመሮች የሚሰሩት በalternating current ብቻ ሲሆን direct current ቮልቴጅን መጨመር ወይም መቀነስ አይችሉም።

ከGrade 12 Physics፣ ገጽ 118-142 የተዘጋጀ፤ ከመውጣቱ በፊት ሁለት ጊዜ ተረጋግጧል

የምዕራፍ 4 የመልመጃ ጥያቄዎች

በዚህ ምዕራፍ ላይ የተጻፉ 10 የምርጫ ጥያቄዎች፣ እያንዳንዳቸው መልሱና ምክንያቱ አላቸው። መልሱን ከመክፈትዎ በፊት ይሞክሩ። ጥያቄዎቹ በእንግሊዝኛ ናቸው።

ጥያቄ 1

What happens if a permanent bar magnet is cut into two equal halves?

A.One piece becomes an isolated north pole and the other an isolated south pole.
B.Each piece becomes a new magnet with both a north pole and a south pole.
C.Both pieces lose their magnetism completely.
D.One piece keeps its poles while the other becomes unmagnetized.

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ B Each piece becomes a new magnet with both a north pole and a south pole.

ምክንያቱ

Magnetic poles are always found in pairs. No matter how many times a permanent magnet is cut into two, each piece always has a north and a south pole.

ጥያቄ 2

What is the SI unit of magnetic flux?

A.Tesla (T)
B.Gauss (G)
C.Weber (Wb)
D.Newton per coulomb (N/C)

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ C Weber (Wb)

ምክንያቱ

The SI unit of magnetic flux is the Weber (Wb), whereas the SI unit of magnetic field is Tesla (T).

ጥያቄ 3

How does an electromagnet differ from a permanent magnet?

A.An electromagnet loses its magnetism when the electric current is turned off.
B.An electromagnet has only a single magnetic pole.
C.An electromagnet cannot attract magnetic materials like iron.
D.An electromagnet does not produce magnetic field lines.

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ A An electromagnet loses its magnetism when the electric current is turned off.

ምክንያቱ

An electromagnet generates a magnetic field only when an electric current is supplied to it, and it loses its magnetism when the current is switched off.

ጥያቄ 4

Which of the following is a correct difference between electric field lines and magnetic field lines?

A.Electric field lines form closed loops, but magnetic field lines do not.
B.Magnetic field lines can cross each other, but electric field lines cannot.
C.Magnetic field lines form continuous closed loops without beginning or end.
D.Electric field lines never start or end on electric charges.

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ C Magnetic field lines form continuous closed loops without beginning or end.

ምክንያቱ

Unlike electric field lines (which start on positive charges and end on negative charges), magnetic field lines form continuous closed loops without a starting or ending point.

ጥያቄ 5

A student in Hawassa observes that a long straight wire carrying a steady current produces a magnetic field of 0.8 T at a distance of 0.5 cm from the wire. What is the magnetic field strength at a distance of 1.0 cm from the same wire?

A.1.6 T
B.0.8 T
C.0.4 T
D.0.2 T

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ C 0.4 T

ምክንያቱ

The magnetic field B around a long straight wire is inversely proportional to the distance r (B = μ₀I / (2πr)). When distance doubles from 0.5 cm to 1.0 cm, the magnetic field is halved: 0.8 T / 2 = 0.4 T.

ጥያቄ 6

Which statement correctly describes the Earth's magnetic poles relative to its geographic poles?

A.The Earth's North magnetic pole corresponds to the South Geographic Pole.
B.The Earth's North magnetic pole corresponds to the North Geographic Pole.
C.The Earth has only a single magnetic pole located at the equator.
D.The Earth's magnetic poles rotate continuously around the equator.

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ A The Earth's North magnetic pole corresponds to the South Geographic Pole.

ምክንያቱ

The Earth behaves like a giant bar magnet inside, where the North magnetic pole corresponds to the South Geographic Pole and vice versa.

ጥያቄ 7

A rectangular card with dimensions 3 cm by 2 cm is held perpendicular to a uniform magnetic field of 0.1 T. What is the magnetic flux passing through the card?

A.6.0 × 10-5 Wb
B.6.0 × 10-1 Wb
C.6.0 × 10-3 Wb
D.6.0 × 10-7 Wb

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ A 6.0 × 10-5 Wb

ምክንያቱ

Area A = 0.03 m × 0.02 m = 6.0 × 10^-4 m². Since the plane is perpendicular to the field, θ = 0° (cos 0° = 1). Therefore, Φ_B = B × A = 0.1 T × 6.0 × 10^-4 m² = 6.0 × 10^-5 Wb.

ጥያቄ 8

Lenz's law, which determines the direction of an induced current, is a consequence of which fundamental principle?

A.Conservation of electric charge
B.Conservation of energy
C.Conservation of mass
D.Conservation of linear momentum

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ B Conservation of energy

ምክንያቱ

Lenz's law states that the induced current opposes the change that creates it, which directly follows from the principle of conservation of energy (and Newton's third law).

ጥያቄ 9

A coil consisting of 500 turns develops an average induced electromotive force (emf) of 60 V. Over what time interval must a magnetic flux change of 0.06 Wb occur across the coil?

A.0.10 s
B.0.50 s
C.2.00 s
D.5.00 s

መልሱንና ምክንያቱን ያሳዩ

መልስ፦ B 0.50 s

ምክንያቱ

Using Faraday's law: |ε| = N × (ΔΦ_B / Δt). Rearranging for Δt gives Δt = (N × ΔΦ_B) / |ε| = (500 × 0.06 Wb) / 60 V = 30 / 60 = 0.50 s.

ጥያቄ 10

In an electrical workshop in Addis Ababa, a technician uses a transformer with 500 primary loops and 5000 secondary loops. If the primary alternating input voltage is 220 V, what is the output voltage from the secondary coil?