ECAT (Engineering College Admission Test)
University of Engineering & Technology (UET), Lahore
UET Lahore ECAT Test Space for preparation together
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When a helium atom loses an electron, it becomes a positively charged ion (He⁺), also known as a positive helium ion. It is not an alpha particle (which consists of 2 protons and 2 neutrons), nor a proton (which is a hydrogen nucleus), nor a negative ion (which would require gaining an electron).
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Beta particles (β-) are high-energy, high-speed electrons emitted by the nucleus during radioactive decay, specifically from the transformation of a neutron into a proton within the nucleus, releasing an electron (beta particle) and an antineutrino.
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An electric charge in uniform motion produces both electric and magnetic fields. The moving charge creates an electric field due to its charge and a magnetic field due to its motion.
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A hot metal filament in a cathode ray tube emits electrons. These emitted electrons form the cathode rays that travel from the cathode to the anode within the tube.
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The time period of a simple pendulum is given by 𝑇 = 2𝜋 √
𝐿 / g, where 𝐿 is the length of the pendulum and 𝑔 is the acceleration due to gravity. The mass of the bob does not affect the time period of the pendulum.
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Newton's rings are a pattern of interference fringes. The center of Newton's rings appears dark because of destructive interference between the light waves reflected from the top and bottom surfaces of the thin air film between the lens and the glass plate.
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The most stable element on the basis of binding energy per nucleon is iron (Fe). The binding energy per nucleon reaches a maximum for iron-56, which means it is the most stable nucleus. This concept is crucial in nuclear physics, as it explains why nuclear fusion occurs in stars up to iron and why heavier elements are formed by supernovae explosions.
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The time constant (𝜏) for an RC circuit is given by the product of resistance (R) and capacitance (C): 𝜏 = R⋅C. given 𝜏 = 2 seconds and R = 1000 ohms: C = 𝜏 / R = 2s / 1000 ohms = 0.002 farads = 2000 μfarads however, as 2 μF aligns closely with the other options, we'll check: C = 2s / 1000 ohms = 2 x 10−3 F = 2000 μF
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Lenz's Law states that the direction of the induced electromotive force (emf) will always be such that it opposes the change in magnetic flux that produced it. This is a fundamental principle in electromagnetism and is key to understanding how induction works.
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For inputs A=0 and B=1: NAND gate outputs 1 (since 0 AND 1 is 0, and NOT 0 is 1). XOR gate outputs 1 (since XOR is true when inputs differ)
Hence, the correct option is C) XOR.
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The Balmer series of the hydrogen spectrum lies in the visible region. It involves transitions where the final energy level is n=2, and the initial levels are n>2.
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Particles that experience the strong nuclear force are nucleons, i.e., protons and neutrons. This force binds the nucleus together.
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When a ball is thrown upward, its vertical velocity decreases linearly with time due to the constant acceleration of gravity acting downward.
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The force that keeps a particle moving in a circular path and is directed towards the center of the circle is called centripetal force.
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x he potential energy at the top converts to kinetic energy at the bottom. Using energy conservation: mgh = 1/2mv2. v = /2gh and h = 3 x 9.8 = 29.4 m and then v = /2 x 9.8 x 29.4 ~~ 11.4 m / s
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Tuning a radio involves adjusting the frequency of the LC circuit to resonate at the frequency of the desired radio station.
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A standing wave on a string fixed at both ends forms when the length of the string is an integral multiple of half wavelengths.
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Infra-red light travels fastest in optical fibers due to lower attenuation and dispersion compared to visible light.
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Kirchhoff's second rule, also known as the voltage law (KVL), states that the sum of the electrical potential differences (voltages) around any closed circuit is zero.
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In an LED, when an electron recombines with a hole in the p-n junction, energy is released in the form of a photon, emitting visible light.
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NH4Cl (Ammonium chloride) exhibits multiple types of bonding:
Ionic Bonding: Between NH4+ (ammonium ion) and Cl- (chloride ion).
Covalent Bonding: Within the NH4+ ion itself, between nitrogen and hydrogen atoms.
Coordinate Covalent Bonding: One of the N-H bonds in NH4+ is formed by nitrogen donating a lone pair to a hydrogen ion (H+).
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During the electrolysis of CuSO4 using copper electrodes:
At the cathode (negative electrode), copper ions (Cu2+) from the solution are reduced to copper metal (Cu):
Cu
2
+
+
2
e
−
→
Cu
Cu
2+
+2e
−
→Cu
At the anode (positive electrode), copper metal dissolves into the solution as Cu2+ ions:
Cu
→
Cu
2
+
+
2
e
−
Cu→Cu
2+
+2e
−
Thus, copper metal deposits on the cathode.
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Aldehydes are synthesized by the oxidation of primary alcohols. The oxidation process involves removing hydrogen atoms from the primary alcohol, forming an aldehyde. For example, the oxidation of ethanol (a primary alcohol) produces acetaldehyde:
CH
3
CH
2
OH
→
CH
3
CHO
+
H
2
O
CH
3
CH
2
OH→CH
3
CHO+H
2
O
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During fermentation, sugars such as glucose are converted by yeast or bacteria into ethanol and carbon dioxide. The general equation for this process is:
C
6
H
12
O
6
→
2
C
2
H
5
OH
+
2
CO
2
C
6
H
12
O
6
→2C
2
H
5
OH+2CO
2
Thus, the products of sugar fermentation are ethanol (C2H5OH) and carbon dioxide (CO2).
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The tetrahedral shape is like a pyramid with a triangular base, where the carbon atom sits in the middle and the four hydrogen atoms form the corners. This shape minimizes the repulsion between the four bonding pairs of electrons.
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A strong acid, like hydrochloric acid, is like a superhero that gives away all of its protons in water. It dissociates completely, making the solution very acidic, while weak acids only give away some protons.
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The carbon atoms in ethene are like juggling three balloons ? they need three bonds in a flat shape. So, they use "sp2" hybrid orbitals, which combine one s orbital and two p orbitals, leaving one p orbital for the double bond.
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Hydrogen bonding is like a very strong handshake between molecules that have hydrogen attached to highly electronegative atoms like nitrogen, oxygen, or fluorine. In NH3, the hydrogen bonds with nitrogen, making a strong connection.
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Evaporation is like when you leave a puddle of water on a sunny day, and it disappears even though it never boiled. The molecules with the most energy escape from the liquid into the air, turning into gas.
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Boyle's Law is like squeezing a balloon. When you press down (increase pressure), the balloon shrinks (volume decreases). The pressure and volume of a gas move in opposite directions when temperature stays the same.
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Electronegativity is like the element?s desire to steal an electron. Fluorine is the most ?greedy? element, meaning it attracts electrons more strongly than any other element on the periodic table.
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Hydrogenation is like smoothing out wrinkles in fabric. The double bond in 2-butene is ?flattened? into a single bond, turning the molecule into butane, a saturated hydrocarbon.
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Solubility in water is like trying to dissolve sugar in tea. Some salts dissolve easily, but AgCl doesn?t. It forms a solid precipitate because its ions don?t separate easily in water, unlike salts like NaCl.
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In beta decay, it's like the nucleus of an atom suddenly ejects an electron (beta particle) to become more stable. A neutron in the nucleus turns into a proton, and the electron is released.
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Oxidation state is like counting the charges sulfur carries. In H2SO4, sulfur has to balance the negative charges from the oxygen atoms, so it "gives away" six electrons, giving it an oxidation state of +6.
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Reduction is like adding extra electrons to a molecule. In this case, you're adding hydrogen to a ketone, converting it into an alcohol. This process usually involves a reducing agent like NaBH4.
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A buffer solution is like a shock absorber for pH. Even if you add a little acid or base, it keeps the pH stable because it contains both a weak acid and its conjugate base (or a weak base and its conjugate acid).
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Charles? Law is like a balloon in the sun ? as the gas inside heats up, the balloon gets bigger. It says that when the temperature of a gas increases, its volume also increases, as long as pressure stays constant.
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The coordination number is like counting how many hands are holding onto the central metal. In this case, cobalt (Co) is held by six ammonia (NH3) molecules, so its coordination number is 6.
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A Lewis acid is like an empty seat waiting for someone to sit down. It accepts a pair of electrons, whereas a Lewis base is like the person offering the electrons to fill the seat.
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The anode is like a battery losing charge. In a galvanic cell, oxidation occurs at the anode, meaning electrons are lost and flow toward the cathode, where reduction happens.
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The empirical formula is like a recipe with the simplest ingredients. This compound?s simplest ratio of carbon, hydrogen, and oxygen comes out to be CH2O, meaning for every carbon atom, there are two hydrogens and one oxygen.
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In an electrolytic cell, reduction happens at the cathode, which is like gaining electrons. The electrons are added to ions or atoms, reducing them to a lower oxidation state.
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Hydrogen bonding is like a super strong handshake between molecules where hydrogen is involved with highly electronegative elements like oxygen or nitrogen. This makes the bonds stronger than other forces like dipole-dipole or dispersion.