Electricity - Class 10 - Science
Renews every month. Cancel anytime
Your personal doubt-solving assistant
Chatterbot AI gives you 100% accurate answers to your questions in an instant.
Back Questions - Electricity | NCERT | Science | Class 10
A piece of wire of resistance $R$ is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is $R^{\prime}$, then the ratio $R / R^{\prime}$ is -
(a) $1 / 25$
(b) $1 / 5$
(c) 5
(d) 25
When a wire of resistance $R$ is cut into five equal parts, the length of each part becomes $1/5$ of the original length. Since the resistance $R$ of a wire is directly proportional to its length $(l)$, given by the formula $R = \rho \cdot (l/A)$ where $\rho$ is the resistivity of the material and (A) is the cross-sectional area, each part will have a resistance of (R/5) because the resistivity and cross-sectional area remain unchanged.
When these parts are connected in parallel, the equivalent resistance $R'$ can be found using the formula for parallel resistances:
$$\frac{1}{R'} = \frac{1}{R/5} + \frac{1}{R/5} + \frac{1}{R/5} + \frac{1}{R/5} + \frac{1}{R/5}$$
$$\frac{1}{R'} = 5 \cdot \frac{1}{R/5}$$
$$\frac{1}{R'} = \frac{5}{R/5}$$
$$\frac{1}{R'} = \frac{25}{R}$$
Therefore,
$$R' = \frac{R}{25}$$
The ratio $R / R'$ can then be calculated as follows:
$$R / R' = R / \left( \frac{R}{25} \right) = 25$$
Thus, the correct answer is (d) 25.
Which of the following terms does not represent electrical power in a circuit?
(a) $I^{2} R$
(b) $I R^{2}$
(c) $V I$
(d) $V^{2} / R$
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowAn electric bulb is rated $220 \mathrm{~V}$ and $100 \mathrm{~W}$. When it is operated on $110 \mathrm{~V}$, the power consumed will be -
(a) $100 \mathrm{~W}$
(b) $75 \mathrm{~W}$
(c) $50 \mathrm{~W}$
(d) $25 \mathrm{~W}$
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowTwo conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be -
(a) $1: 2$
(b) $2: 1$
(c) $1: 4$
(d) 4:1
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowHow is a voltmeter connected in the circuit to measure the potential difference between two points? (80 words)
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowA copper wire has diameter $0.5 \mathrm{~mm}$ and resistivity of $1.6 \times 10^{-8} \Omega \mathrm{m}$. What will be the length of this wire to make its resistance $10 \Omega$ ? How much does the resistance change if the diameter is doubled?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowThe values of current $I$ flowing in a given resistor for the corresponding values of potential difference $V$ across the resistor are given below -
$I$ (amperes) | 0.5 | 1.0 | 2.0 | 3.0 | 4.0 |
$V$ (volts) | 1.6 | 3.4 | 6.7 | 10.2 | 13.2 |
Plot a graph between $V$ and $I$ and calculate the resistance of that resistor.
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowWhen a $12 \mathrm{~V}$ battery is connected across an unknown resistor, there is a current of $2.5 \mathrm{~mA}$ in the circuit. Find the value of the resistance of the resistor.
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowA battery of $9 \mathrm{~V}$ is connected in series with resistors of $0.2 \Omega, 0.3 \Omega, 0.4 \Omega, 0.5 \Omega$ and $12 \Omega$, respectively. How much current would flow through the $12 \Omega$ resistor?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowHow many $176 \Omega$ resistors (in parallel) are required to carry $5 \mathrm{~A}$ on a $220 \mathrm{~V}$ line?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowShow how you would connect three resistors, each of resistance $6 \Omega$, so that the combination has a resistance of (i) $9 \Omega$, (ii) $4 \Omega$.
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowSeveral electric bulbs designed to be used on a $220 \mathrm{~V}$ electric supply line, are rated $10 \mathrm{~W}$. How many lamps can be connected in parallel with each other across the two wires of $220 \mathrm{~V}$ line if the maximum allowable current is $5 \mathrm{~A}$ ?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowA hot plate of an electric oven connected to a $220 \mathrm{~V}$ line has two resistance coils A and B, each of $24 \Omega$ resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowCompare the power used in the $2 \Omega$ resistor in each of the following circuits: (i) a $6 \mathrm{~V}$ battery in series with $1 \Omega$ and $2 \Omega$ resistors, and (ii) a $4 \mathrm{~V}$ battery in parallel with $12 \Omega$ and $2 \Omega$ resistors.
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowTwo lamps, one rated $100 \mathrm{~W}$ at $220 \mathrm{~V}$, and the other $60 \mathrm{~W}$ at $220 \mathrm{~V}$, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is $220 \mathrm{~V}$ ?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowWhich uses more energy, a $250 \mathrm{~W} \mathrm{TV}$ set in $1 \mathrm{hr}$, or a $1200 \mathrm{~W}$ toaster in 10 minutes?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowAn electric heater of resistance $8 \Omega$ draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowExplain the following.
(a) Why is the tungsten used almost exclusively for filament of electric lamps?
(b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its area of cross-section?
(e) Why are copper and aluminium wires usually employed for electricity transmission?
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowExtra Questions - Electricity | NCERT | Science | Class 10
When a $12 \mathrm{~V}$ battery is connected across an unknown resistor, there is a current of 2.5 $\mathrm{mA}$ in the circuit. Find the value of the resistance of the resistor.
A) $4.8 \Omega$
B) $50 \Omega$
C) $4800 \Omega$
D) $5000 \Omega$
Using Ohm's Law, which is represented by the formula: $$ V = IR $$ Here, the voltage ($V$) is given as $12 \text{ V}$, and the current ($I$) is $2.5 \text{ mA}$.
First, converting the current from milliamperes to amperes: $$ I = 2.5 \text{ mA} = 2.5 \times 10^{-3} \text{ A} $$
Now, we can solve for the resistance ($R$) using the formula for Ohm's Law: $$ R = \frac{V}{I} = \frac{12 \text{ V}}{2.5 \times 10^{-3} \text{ A}} = 4800 \Omega $$
Thus, the value of the resistance is $4800 \Omega$, corresponding to option C.
The voltage across each appliance connected in series is different.
A) True
B) False
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up now"It is dangerous to connect the switch in the neutral wire. Explain your answer."
Improve your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up nowImprove your grades!
Join English Chatterbox to access detailed and curated answers, and score higher than you ever have in your exams.
Sign up now