Class Nine Electricity and magnetism

Students click below to run simulation

Electromagnetic Induction

This describes how electricity is produced. This law is known as faraday law of electromagnetic induction. Move the magnet and change the controls

STATIC ELECTRICITY

Rub the baloon on the sweater

Creating a circuit (Virtual Lab)

Select the components from the left side and connect with connecting wires

Ohm's Law

Change the value of Voltage and keeping resistance constant and observe the current, and plot a graph

Variation of Resistance

Change the different parameters to observe how resistance of a conductor depends upon different factors

Tissue

 

Anatomy and Primary Structure of Monocot Stem-maize Stem

The outline of the maize in transverse section is more or less circular.

 

Primary Structure of Monocot Stem-maize Stem

 

The outline of the maize in transverse section is more or less circular. The transverse section of the monocot stem [maize] shows the following plan of arrangement of tissues from the periphery to the centre.

 Epidermis

 It is the outermost layer of the stem. It is made up of single layer of tightly packed parenchymatous cells. Their outer walls are covered with thick cuticle. The continuity of this layer may be broken here and there by the presence of a few stomata. There are no epidermal outgrowths.

 Hypodermis

 A few layer of sclerenchymatous cells lying below the epidermis constitute the hypodermis. This layer gives mechanical strength to the  plant. It is interrupted here and there by chlorenchyma cells.

 Ground Tissue

 There is no distinction into cortex, endodermis, pericycle and pith. The entire mass of parenchyma cells lying inner to the hypodermis forms the ground tissue.

The cell wall is made up of cellulose. The cells contain reserve food material like starch. The cells of the ground tissue next to the hypodermis are smaller in size, polygonal in shape and compactly arranged.

Towards the centre, the cells are loosely arranged, rounded in shape and bigger in size. The vascular bundles lie embedded in this tissue. The ground tissue stores food and performs gaseous exchange.

Vascular Bundles

Vascular bundles are scattered (atactostele) in the parenchymatous ground tissue. Each  vascular bundle is surrounded by a sheath of sclerenchy-matousfibres called bundle sheath. The vascular bundles areconjoint, collateral, endarch and closed.Vascular bundles are numerous, small and closely arranged in the peripheral portion. Towards the cen-tre, the bundles are comparatively large in size and loosely arranged­. Vascular bun-dles are skull or oval shaped.

 Phloem

The phloem in the monocot stem consists of sieve tubes and companion cells. Phloem parenchyma and phloem fibres are absent. It can be distinguished into an outer crushed protophloem and an inner metaphloem.

 Xylem

 Xylem vessels are arranged in the form of ’Y’ the two metaxylem vessels are located at the upper two arms and one or two protoxylem vessels at the base. In a mature bundle, the lowest protoxylem disintegrates and forms a cavity known as protoxylem lacuna.

 

Anatomical differences between dicot stem and monocot stem

1. Hypodermis

Characters of Dicot Stem :Collenchymatous

Characters of Monocot Stem :Sclerenchymatous

2. Ground tissue

Characters of Dicot Stem : Differentiated into cortex, endodermis and pericycle and pith

Characters of Monocot Stem : Not differentiated, but it is a continuous mass of parenchyma

3. Starch Sheath

Characters of Dicot Stem : Present

Characters of Monocot Stem : Absent

4. Medullary rays

Characters of Dicot Stem : Present

Characters of Monocot Stem : Absent

5. Vascular bundles

Characters of Dicot Stem : (a) Collateral and open

Characters of Monocot Stem : (a) Collateral and closed

 Characters of Dicot Stem : (b) Arranged in a ring

Characters of Monocot Stem : (b) Scattered in ground tissue

 Characters of Dicot Stem : (c) Secondary growth occurs

Characters of Monocot Stem : (c) Secondary growth usually does not occur.

Anatomical differences between root and stem

  

 1. Epidermis 

Root : Absence of cuticle and epidermal pores.

Stem : Presence of cuticle and epidermal pores.

Root : Presence of unicellular root hairs.

Stem : Presence of unicellular and multicellular trichomes

2. Outer Cortical cells

Root :Chlorenchyma absent 

Stem :Chlorenchyma present

3. Endodermis 

Root : Well defined 

Stem : ill-defined or absent.

4. Vascular bundles

Root : Radial arrangement 

Stem : Conjoint arrangement

5. Xylem 

Root : Exarch 

Stem :Endarch

Dicot Root

Monocot Root

Scientific learning

 Scientific Study

The scientific method is the process of objectively establishing facts through testing and experimentation. The basic process involves making an observation, forming a hypothesis, making a prediction, conducting an experiment and finally analyzing the results. The principals of the scientific method can be applied in many areas, including scientific research, business and technology.

Variables in Scientific Study

As we know scientific study involve process of observation and experimentation, we need to consider some physical quantities that we observe , manipulate or keep consant during our study. Those measurable quantities are called Variables. 

Types of Variables

• Independent Variable
• Dependent Variable
• Control Variable

Example 1.1

Let us consider an experiment in which we are studying the effect on growth of plant with the use of fertilizer.

• Here We are observing the "growth of plant" so it is dependent variable.
• In this experiment we study the " growth of plant by changing the amount of "fertilizer" so it is dependent variable.
• The growth of plant also depends upon other factors also like type of seed, amount of water, type of soil etc. So while studying the effect of fertilizer (independent variable), we keep those varables constant. Such variables are called control variable.

Independent Variable

An independent variable is the variable we manipulate or vary in an experimental study to explore its effects. It’s called “independent” because it’s not influenced by any other variables in the study.

Dependent Variable

A dependent variable is the variable that changes as a result of the change in independent variable. It is what we are  interested to study, and it “depends” on  independent variable.

Experiment / problem	Independent variable	Dependent variable(s)
Do tomatoes grow fastest under fluorescent, incandescent, or natural light?	Type of light the tomato plant is grown under	The rate of growth of the tomato plant
What is the effect of intermittent fasting on blood sugar levels?	Presence or absence of intermittent fasting	Blood sugar levels
Is medical marijuana effective for pain reduction in people with chronic pain?	Presence or absence of medical marijuana use	Frequency of pain Intensity of pain
To what extent does remote working increase job satisfaction?	Type of work environment (remote or in office)	Job satisfaction self-reports

Difference Between Dependent and Independent Variable

Independent Variable	Dependent Variable
An Independent variable is a variable whose value never depends on another variable.	A dependent variable is a variable whose value depends on another variable.
The Independent variable is the presumed cause.	The dependent variable is the presumed effect.
Any change in the independent variable also affects the dependent variable.	Dependent variable changes, then the independent variable will not be affected.
Independent variables are the predictors or regressors.	Dependent variables are often referred as the predicted variable.
Independent variables can become easily obtainable and do not need any complex mathematical procedures and observations.	Dependent variables are obtained from longitudinal research or by solving complex mathematical equations.
Independent variables are can be manipulated by the researcher. So he or she is biased. Then it may affect the results of the research.	You cannot be manipulated by the research or any other external factor.
Independent variables are positioned horizontally on the graph.	Dependent variables are positioned vertically on the graph.

Control Variable

A control variable is anything that is held constant or limited in a research study. It’s a variable that is not of interest to the study’s objectives, but is controlled because it could influence the outcomes.

Points to be considered in variables

1. In an experiment or research there must a single independent variable.
2. In an experiment or research there must be a single dependent variable.
3. All other variables except dependent and independent variables must be kept constant.
4. While writing variables in the form of mathematical equation, independent variable should be on right side and dependent variable on left. e.g 
   s = vt    ( s ∝ t)
   we are studying the distance covered by a vehicle in different time keeping the velocity constant. 
   so, t= independent variable
        s = dependent variable
        v = control variable
5. In a graph independent varaible is always in x- axis and dependent variable is always in y axis. So a graph shows the variation of dependent variable (x-axis ) with change in independent variable (y-axis).
   
   
   
6. 
   

Math 2

 

Math 1

 

Nepali 1

 

Class 10 Science (1Marks) Physics

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Science Practice Exam 10

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Force Note

Here is a complete note on chapter one force.

Question Electricity and magnetism

d) What type of combination of cells is shown in the given circuit? Calculate the power of the bulb if 0.2Acurrent flows through the curcuit.

 

Answer the  following questions:

a) What is ment by one kilowatt hour in electricity?
Ans: The electricity consumed by electric load of load of one kilowatt power in one hour is known as one kilowatt hour in electricity.

b) What is meant by electric current?
Ans: The flow of electron in a conducting wire is known as electric current.

c) What is meant by electric circuit?
Ans: The pathway of electricity containing combination of source, load and switch is known as electricity circuit.

d) What is meant by electricity consumption?
Ans: The amount of electricity which id converted to the other forms of energy  by using load is known as electricity consumption.

e) How is electricity consumption calcutated?
Ans: To claculate the electricity consumption the product of the number of load, power, and time is calculated:
Electricity consumption= P×N×T

f) What is meant by electric power?
Ans: The amount of electric of energy consumd by a load in one second is known as electric power.

g) Which instrument is used to measure the electrical power consumption?
Ans: Meter box is used to measure the electrical power consumption. It measures the power consumption in kilowatt hour.

h)  What is meant by galvanometer?
Ans: The electrical device which is used to measure small signals of current is known as galvanometer.

i) On which principle generator and dynamo depends?
Ans: The working principle of generator and dynamo depends on the principle of electromagnetic induction.

j) What are the types of generator?
Ans: Following are the types of generator:
i. AC generator
ii. DC generator, etc.

Give reasons:

a) The efficiency of a transformer is never 100%, why?
Ans: There is resistance in the coil of a transformer, so the efficiency of a transformer is never 100%.

b) Soft iron armature is used in electric bell, why?
Ans: The more the metal is soft the strength of magnet formed is more. So, soft iron armature is used in electric bell.

c) Filament lamp is filled with inert gases. Why?
Ans: In high temperature i.e. around 2900°C tungsten filament can get oxidised due to reaction with oxygen. So, to prevent oxidation and maintain the pressure, innert gas is filled in filament lamp.

d) Why is Nichrome used in heater?
Ans: Nichrome has high resistance and does not get oxidised even in high temperature like 900°C and can easily converts electric energy into heat energy. So, nichromee is used in heater.

e) Why should the coil of transformer be laminated?
Ans: When curent flows through the coil of transformer, eddy current is produced in the core. If the coil of transformer becomes a single piece, the amount of eddy current increases and the transformer gets heated and damaged. Output is also low. So, the  coil of transformer is laminated.

Differentiate between:

a) Phase wire and Neutral wire
Ans: Following are the differentiate between on phase and neutral wire:

Phase wire	Neutral wire
It is a red/ brown colored wire connected electrical device (load) to input current.	It is a black or blue colored wire through which current from load returns back.
We feel electric on touching it.	We feel electric on touching it.

Numerical problems:

i. Power consumption (pc): Power (P) × Hour(H)
=Watt × Hours
= KWH
=Unit

ii. Watt = Volt × Amper
Power = Volt (V) × current (Amper)
According to ohm’s law:
V = IR
PD = Current × Resistance
Volt     Amper      ohm (Ω)

a) An electric kettle rated 220 V and 2.2 KW works for 3 hours. Find the energy consumption and current drawn by it.
Given data,
PD = 220 volt
Power= 2.2 kw
Time = 3 hours
We know that,

Power consumption= power × hour
= 2.2kw × 3 hour
=6.6 KWH
= 6.6 Unit

Again, current drawn (I)= ?
P=VI
∴ I = P/V = 2.2 × 100W/ 220 = 2200/220
=10 AMP

∴The energy consumption is 6.6 unit and current drawn by it is 10 AMP.

b) If a 1000W heater is to be operated at a 220V mains, what must be the rating of the force to be used in the circuit?
Given data,
P = 1000 W
PD= 220V
Fuse (I)= ?
We know that,
P =VI
∴I = P/V= 1000/220
=50/11 = 4.5 = 5AMP

∴So the 5AMP is the rating of the force to be used in the circuit.

c) If two irons of 750W each are used 8hours a month. How much tariff should be paid? Cost of one unit of electricity is Rs 7.
Given data,
P= 750W
T=2 month
N= 8 hours
We know that,
Power consumption= 750 × 8 × 2
= 2 × 750 × 8/ 1000
= 12 KHW
=2 unit

∴ The cost of 1 unit= Rs. 7.00
∴The cost of 12 unit = 12×7 = Rs. 84.00

d) What type of combination of cells is shown in the given circuit? Calculate the power of the bulb if 0.2Acurrent flows through the curcuit.

Given data,
Amp= 0.2
Volt = 6
We know that,
Watt= Volt × Amp
= 6×0.2
=1.2 watt

e) In a transformer, the number of turns in primary coil is 100. If the primary and secondary voltage are 220V and 110V respecctively, calculate the no of turns in the secondary coil.
Given data,
Np= 100
Vp= 220 volt
Vs= 110 volt
Ns=?
we know that,