Current Flashcards
If a charge of 25 C passes a given point in a circuit in a time of 125 ms, determine the current in the circuit.
200 A
Current (I) can be calculated using the formula I = Q/t, where Q is charge and t is time.
If a current of 5A flows through a conductor, the time taken for 31.21 x 10^18 electrons to pass through a point is?
1.2 s
This can be calculated by using the relation between current, charge, and time.
If a current of 5A flows through a conductor, how many electrons pass through a point in 1 second?
31.21 x 10^18 e
This is derived from the charge passing through, where 1 C = 6.242 x 10^18 e.
If a current of 10A flows through a conductor, how many coulombs pass through a point in 2 seconds?
20 C
Current (I) is defined as charge (Q) per unit time (t).
In metallic conductors, current is due to the flow of?
Electrons
The unit of electrical quantity is?
Coulomb
The unit of electric charge is?
Coulomb
Other units include Ampere second and Faraday.
What is 1 ampere hour in coulombs?
3600 C
1 ampere hour = 1 A x 3600 s.
Find the potential difference if 60 J of energy are utilized by a charge of 20 C.
3 V
Potential difference (V) can be calculated using the formula V = E/Q.
Determine the energy required in moving a charge of 50 µC through a potential difference of 6 V.
300 μJ
Energy (E) is calculated using E = QV.
How much electrical energy is consumed in an electric iron rated as 750W/250V used for 90 minutes?
1.125 kWh
Energy consumed can be calculated using the formula E = P x t.
Commercial unit of Electrical energy is?
Kilo watt hour
One Coulomb per second is?
1 Ampere
One Watt is?
1 J/S
What is the unit of work done in SI units?
Joule
One metric HP is equal to?
746 W
Electrical energy is measured in?
kWh
Energy consumed by a 100 W bulb in 10 hours is?
1 kWh
1 eV is equal to?
1.602 x 10^-19 J
Which of the following statements are true regarding resistivity?
Resistivity depends on the temperature
Resistivity is generally a function of material type and temperature.
The condition for the validity under ohm’s law is that the?
Current should be proportional to voltage
The relation between voltage, current, and resistance in a closed circuit is given as?
I = V/R
If in a closed circuit the voltage is reduced to half and resistance is doubled, the current becomes?
A quarter
The curve representing ohm’s law is?
Linear
A linear resistor is one which obeys?
Ohm’s law
The specific resistance depends on?
All of the above
Specific resistance depends on length, cross-section, and material.
If the diameter of a metal wire of a given length is doubled, then its resistance will?
Halved
The formula to find the temperature coefficient of resistance of a material is?
R₁ = R₀(1 + αt)
The unit of resistivity is?
Ωm
The formula to find the specific resistance (ρ) where length (l), cross-sectional area (A), and resistance (R)?
ρ = R(A/l)
The temperature coefficient of resistance of an insulator is?
Negative
If the length of a wire of resistance 100 ohms is uniformly stretched to 2 times its original length, the new resistance of the wire is?
400 ohms
If the length of a wire of resistance R is uniformly stretched to n times its original length, the new resistance of the wire is?
n²R
The heating element in an electric heater is made up of which material?
Nichrome
A heater coil is cut into two equal parts. What is the ratio of heat produced by one half cut coil to that of the original coil?
1:2
The heating element of an electric heater should be made with a material, which should have?
High specific resistance and high melting point
An open circuit can have a potential difference across its terminals, but the current is always?
Zero amperes
A short circuit can have a potential difference across its terminals, but the current is always?
Finite current and finite voltage
In a closed loop of a D.C. circuit, the algebraic sum of the e.m.fs is equal to?
Zero
Using Kirchhoff’s voltage law, the unknown voltages for the network can be determined by?
Applying the law to each loop in the circuit
What is the formula for calculating the energy dissipated in a resistor over time?
Energy = Power × Time
Energy is measured in joules, power in watts, and time in seconds.
If two electric bulbs have tungsten filament of the same thickness and one gives 60 W while the other gives 100 W, which statement is true?
c) 100 W lamp filament has longer length
Higher wattage indicates a longer filament due to increased resistance.
What is the combined resistance of four resistors with values of 20 ohm, 40 ohm, 50 ohm, and 200 ohm connected in parallel?
10 ohm
The formula for combined resistance in parallel is 1/R_total = 1/R1 + 1/R2 + 1/R3 + 1/R4.
When a 200 W, 200 V bulb and a 100 W, 200 V bulb are connected in series with a total voltage of 400 V applied, which bulb will be brighter?
b) 200 W bulb will be brighter than 100 W bulb
In series, the power ratings affect the brightness due to voltage division.
Fill in the blank: If one bulb has a power rating of 60 W and the other has 100 W, the _______ lamp filament has longer length.
100 W
This is due to the relationship between power, resistance, and filament length.
True or False: The 60 W and 100 W lamp filaments have equal length.
False
The filament length varies with the wattage due to resistance differences.
